ArrayList.cs source code in C# .NET

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Code:

/ FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Collections / ArrayList.cs / 1 / ArrayList.cs

                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
/*============================================================
** 
** Class:  ArrayList 
**
** 
** Purpose: Implements a dynamically sized List as an array,
**          and provides many convenience methods for treating
**          an array as an IList.
** 
**
===========================================================*/ 
namespace System.Collections { 
    using System;
    using System.Security.Permissions; 
    using System.Diagnostics;
    using System.Runtime.Serialization;

    // Implements a variable-size List that uses an array of objects to store the 
    // elements. A ArrayList has a capacity, which is the allocated length
    // of the internal array. As elements are added to a ArrayList, the capacity 
    // of the ArrayList is automatically increased as required by reallocating the 
    // internal array.
    // 
    [DebuggerTypeProxy(typeof(System.Collections.ArrayList.ArrayListDebugView))]
    [DebuggerDisplay("Count = {Count}")]
    [Serializable()]
[System.Runtime.InteropServices.ComVisible(true)] 
    public class ArrayList : IList, ICloneable
    { 
        private Object[] _items; 
        private int _size;
        private int _version; 
        [NonSerialized]
        private Object _syncRoot;

        private const int _defaultCapacity = 4; 
        private static readonly Object[] emptyArray = new Object[0];
 
        // Note: this constructor is a bogus constructor that does nothing 
        // and is for use only with SyncArrayList.
        internal ArrayList( bool trash ) 
        {
        }

        // Constructs a ArrayList. The list is initially empty and has a capacity 
        // of zero. Upon adding the first element to the list the capacity is
        // increased to _defaultCapacity, and then increased in multiples of two as required. 
        public ArrayList() { 
            _items = emptyArray;
        } 

        // Constructs a ArrayList with a given initial capacity. The list is
        // initially empty, but will have room for the given number of elements
        // before any reallocations are required. 
        //
         public ArrayList(int capacity) { 
            if (capacity < 0) throw new ArgumentOutOfRangeException("capacity", Environment.GetResourceString("ArgumentOutOfRange_MustBeNonNegNum", "capacity")); 
            _items = new Object[capacity];
        } 

        // Constructs a ArrayList, copying the contents of the given collection. The
        // size and capacity of the new list will both be equal to the size of the
        // given collection. 
        //
        public ArrayList(ICollection c) { 
            if (c==null) 
                throw new ArgumentNullException("c", Environment.GetResourceString("ArgumentNull_Collection"));
            _items = new Object[c.Count]; 
            AddRange(c);
        }

        // Gets and sets the capacity of this list.  The capacity is the size of 
        // the internal array used to hold items.  When set, the internal
        // array of the list is reallocated to the given capacity. 
        // 
         public virtual int Capacity {
            get { return _items.Length; } 
            set {
                // We don't want to update the version number when we change the capacity.
                // Some existing applications have dependency on this.
                if (value != _items.Length) { 
                    if (value < _size) {
                        throw new ArgumentOutOfRangeException("value", Environment.GetResourceString("ArgumentOutOfRange_SmallCapacity")); 
                    } 

                    if (value > 0) { 
                        Object[] newItems = new Object[value];
                        if (_size > 0) {
                            Array.Copy(_items, 0, newItems, 0, _size);
                        } 
                        _items = newItems;
                    } 
                    else { 
                        _items = new Object[_defaultCapacity];
                    } 
                }
            }
        }
 
        // Read-only property describing how many elements are in the List.
        public virtual int Count { 
            get { return _size; } 
        }
 
        public virtual bool IsFixedSize {
            get { return false; }
        }
 

        // Is this ArrayList read-only? 
        public virtual bool IsReadOnly { 
            get { return false; }
        } 

        // Is this ArrayList synchronized (thread-safe)?
        public virtual bool IsSynchronized {
            get { return false; } 
        }
 
        // Synchronization root for this object. 
        public virtual Object SyncRoot {
            get { 
                if( _syncRoot == null) {
                    System.Threading.Interlocked.CompareExchange(ref _syncRoot, new Object(), null);
                }
                return _syncRoot; 
            }
        } 
 
        // Sets or Gets the element at the given index.
        // 
        public virtual Object this[int index] {
            get {
                if (index < 0 || index >= _size) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index"));
                return _items[index]; 
            }
            set { 
                if (index < 0 || index >= _size) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index")); 
                _items[index] = value;
                _version++; 
            }
        }

        // Creates a ArrayList wrapper for a particular IList.  This does not 
        // copy the contents of the IList, but only wraps the ILIst.  So any
        // changes to the underlying list will affect the ArrayList.  This would 
        // be useful if you want to Reverse a subrange of an IList, or want to 
        // use a generic BinarySearch or Sort method without implementing one yourself.
        // However, since these methods are generic, the performance may not be 
        // nearly as good for some operations as they would be on the IList itself.
        //
        public static ArrayList Adapter(IList list) {
            if (list==null) 
                throw new ArgumentNullException("list");
            return new IListWrapper(list); 
        } 

        // Adds the given object to the end of this list. The size of the list is 
        // increased by one. If required, the capacity of the list is doubled
        // before adding the new element.
        //
        public virtual int Add(Object value) { 
            if (_size == _items.Length) EnsureCapacity(_size + 1);
            _items[_size] = value; 
            _version++; 
            return _size++;
        } 

        // Adds the elements of the given collection to the end of this list. If
        // required, the capacity of the list is increased to twice the previous
        // capacity or the new size, whichever is larger. 
        //
        public virtual void AddRange(ICollection c) { 
            InsertRange(_size, c); 
        }
 
        // Searches a section of the list for a given element using a binary search
        // algorithm. Elements of the list are compared to the search value using
        // the given IComparer interface. If comparer is null, elements of
        // the list are compared to the search value using the IComparable 
        // interface, which in that case must be implemented by all elements of the
        // list and the given search value. This method assumes that the given 
        // section of the list is already sorted; if this is not the case, the 
        // result will be incorrect.
        // 
        // The method returns the index of the given value in the list. If the
        // list does not contain the given value, the method returns a negative
        // integer. The bitwise complement operator (~) can be applied to a
        // negative result to produce the index of the first element (if any) that 
        // is larger than the given search value. This is also the index at which
        // the search value should be inserted into the list in order for the list 
        // to remain sorted. 
        //
        // The method uses the Array.BinarySearch method to perform the 
        // search.
        //
        public virtual int BinarySearch(int index, int count, Object value, IComparer comparer) {
            if (index < 0 || count < 0) 
                throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
            if (_size - index < count) 
                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); 

            return Array.BinarySearch((Array)_items, index, count, value, comparer); 
        }

        public virtual int BinarySearch(Object value)
        { 
            return BinarySearch(0,Count,value,null);
        } 
 
        public virtual int BinarySearch(Object value, IComparer comparer)
        { 
            return BinarySearch(0,Count,value,comparer);
        }

 
        // Clears the contents of ArrayList.
        public virtual void Clear() { 
            Array.Clear(_items, 0, _size); // Don't need to doc this but we clear the elements so that the gc can reclaim the references. 
            _size = 0;
            _version++; 
        }

        // Clones this ArrayList, doing a shallow copy.  (A copy is made of all
        // Object references in the ArrayList, but the Objects pointed to 
        // are not cloned).
        public virtual Object Clone() 
        { 
            ArrayList la = new ArrayList(_size);
            la._size = _size; 
            la._version = _version;
            Array.Copy(_items, 0, la._items, 0, _size);
            return la;
        } 

 
        // Contains returns true if the specified element is in the ArrayList. 
        // It does a linear, O(n) search.  Equality is determined by calling
        // item.Equals(). 
        //
        public virtual bool Contains(Object item) {
            if (item==null) {
                for(int i=0; i<_size; i++) 
                    if (_items[i]==null)
                        return true; 
                return false; 
            }
            else { 
                for(int i=0; i<_size; i++)
                    if ( (_items[i] != null) && (_items[i].Equals(item)) )
                        return true;
                return false; 
            }
        } 
 
        // Copies this ArrayList into array, which must be of a
        // compatible array type. 
        //
        public virtual void CopyTo(Array array) {
            CopyTo(array, 0);
        } 

        // Copies this ArrayList into array, which must be of a 
        // compatible array type. 
        //
        public virtual void CopyTo(Array array, int arrayIndex) { 
            if ((array != null) && (array.Rank != 1))
                throw new ArgumentException(Environment.GetResourceString("Arg_RankMultiDimNotSupported"));
            // Delegate rest of error checking to Array.Copy.
            Array.Copy(_items, 0, array, arrayIndex, _size); 
        }
 
        // Copies a section of this list to the given array at the given index. 
        //
        // The method uses the Array.Copy method to copy the elements. 
        //
        public virtual void CopyTo(int index, Array array, int arrayIndex, int count) {
            if (_size - index < count)
                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); 
            if ((array != null) && (array.Rank != 1))
                throw new ArgumentException(Environment.GetResourceString("Arg_RankMultiDimNotSupported")); 
            // Delegate rest of error checking to Array.Copy. 
            Array.Copy(_items, index, array, arrayIndex, count);
        } 

        // Ensures that the capacity of this list is at least the given minimum
        // value. If the currect capacity of the list is less than min, the
        // capacity is increased to twice the current capacity or to min, 
        // whichever is larger.
        private void EnsureCapacity(int min) { 
            if (_items.Length < min) { 
                int newCapacity = _items.Length == 0? _defaultCapacity: _items.Length * 2;
                if (newCapacity < min) newCapacity = min; 
                Capacity = newCapacity;
            }
        }
 
        // Returns a list wrapper that is fixed at the current size.  Operations
        // that add or remove items will fail, however, replacing items is allowed. 
        // 
        public static IList FixedSize(IList list) {
            if (list==null) 
                throw new ArgumentNullException("list");
            return new FixedSizeList(list);
        }
 
        // Returns a list wrapper that is fixed at the current size.  Operations
        // that add or remove items will fail, however, replacing items is allowed. 
        // 
        public static ArrayList FixedSize(ArrayList list) {
            if (list==null) 
                throw new ArgumentNullException("list");
            return new FixedSizeArrayList(list);
        }
 
        // Returns an enumerator for this list with the given
        // permission for removal of elements. If modifications made to the list 
        // while an enumeration is in progress, the MoveNext and 
        // GetObject methods of the enumerator will throw an exception.
        // 
        public virtual IEnumerator GetEnumerator() {
            return new ArrayListEnumeratorSimple(this);
        }
 
        // Returns an enumerator for a section of this list with the given
        // permission for removal of elements. If modifications made to the list 
        // while an enumeration is in progress, the MoveNext and 
        // GetObject methods of the enumerator will throw an exception.
        // 
        public virtual IEnumerator GetEnumerator(int index, int count) {
            if (index < 0 || count < 0)
                throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
            if (_size - index < count) 
                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
 
            return new ArrayListEnumerator(this, index, count); 
        }
 
        // Returns the index of the first occurrence of a given value in a range of
        // this list. The list is searched forwards from beginning to end.
        // The elements of the list are compared to the given value using the
        // Object.Equals method. 
        //
        // This method uses the Array.IndexOf method to perform the 
        // search. 
        //
        public virtual int IndexOf(Object value) { 
            return Array.IndexOf((Array)_items, value, 0, _size);
        }

        // Returns the index of the first occurrence of a given value in a range of 
        // this list. The list is searched forwards, starting at index
        // startIndex and ending at count number of elements. The 
        // elements of the list are compared to the given value using the 
        // Object.Equals method.
        // 
        // This method uses the Array.IndexOf method to perform the
        // search.
        //
        public virtual int IndexOf(Object value, int startIndex) { 
            if (startIndex > _size)
                throw new ArgumentOutOfRangeException("startIndex", Environment.GetResourceString("ArgumentOutOfRange_Index")); 
            return Array.IndexOf((Array)_items, value, startIndex, _size - startIndex); 
        }
 
        // Returns the index of the first occurrence of a given value in a range of
        // this list. The list is searched forwards, starting at index
        // startIndex and upto count number of elements. The
        // elements of the list are compared to the given value using the 
        // Object.Equals method.
        // 
        // This method uses the Array.IndexOf method to perform the 
        // search.
        // 
        public virtual int IndexOf(Object value, int startIndex, int count) {
            if (startIndex > _size)
                throw new ArgumentOutOfRangeException("startIndex", Environment.GetResourceString("ArgumentOutOfRange_Index"));
            if (count <0 || startIndex > _size - count) throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_Count")); 
            return Array.IndexOf((Array)_items, value, startIndex, count);
        } 
 
        // Inserts an element into this list at a given index. The size of the list
        // is increased by one. If required, the capacity of the list is doubled 
        // before inserting the new element.
        //
        public virtual void Insert(int index, Object value) {
            // Note that insertions at the end are legal. 
            if (index < 0 || index > _size) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_ArrayListInsert"));
            if (_size == _items.Length) EnsureCapacity(_size + 1); 
            if (index < _size) { 
                Array.Copy(_items, index, _items, index + 1, _size - index);
            } 
            _items[index] = value;
            _size++;
            _version++;
        } 

        // Inserts the elements of the given collection at a given index. If 
        // required, the capacity of the list is increased to twice the previous 
        // capacity or the new size, whichever is larger.  Ranges may be added
        // to the end of the list by setting index to the ArrayList's size. 
        //
        public virtual void InsertRange(int index, ICollection c) {
            if (c==null)
                throw new ArgumentNullException("c", Environment.GetResourceString("ArgumentNull_Collection")); 
            if (index < 0 || index > _size) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index"));
            int count = c.Count; 
            if (count > 0) { 
                EnsureCapacity(_size + count);
                // shift existing items 
                if (index < _size) {
                    Array.Copy(_items, index, _items, index + count, _size - index);
                }
 
                Object[] itemsToInsert = new Object[count];
                c.CopyTo(itemsToInsert, 0); 
                itemsToInsert.CopyTo(_items, index); 
                _size += count;
                _version++; 
            }
        }

        // Returns the index of the last occurrence of a given value in a range of 
        // this list. The list is searched backwards, starting at the end
        // and ending at the first element in the list. The elements of the list 
        // are compared to the given value using the Object.Equals method. 
        //
        // This method uses the Array.LastIndexOf method to perform the 
        // search.
        //
        public virtual int LastIndexOf(Object value)
        { 
            return LastIndexOf(value, _size - 1, _size);
        } 
 
        // Returns the index of the last occurrence of a given value in a range of
        // this list. The list is searched backwards, starting at index 
        // startIndex and ending at the first element in the list. The
        // elements of the list are compared to the given value using the
        // Object.Equals method.
        // 
        // This method uses the Array.LastIndexOf method to perform the
        // search. 
        // 
        public virtual int LastIndexOf(Object value, int startIndex)
        { 
            if (startIndex >= _size)
                throw new ArgumentOutOfRangeException("startIndex", Environment.GetResourceString("ArgumentOutOfRange_Index"));
            return LastIndexOf(value, startIndex, startIndex + 1);
        } 

        // Returns the index of the last occurrence of a given value in a range of 
        // this list. The list is searched backwards, starting at index 
        // startIndex and upto count elements. The elements of
        // the list are compared to the given value using the Object.Equals 
        // method.
        //
        // This method uses the Array.LastIndexOf method to perform the
        // search. 
        //
        public virtual int LastIndexOf(Object value, int startIndex, int count) { 
            if (_size == 0) 
                return -1;
            if (startIndex < 0 || count < 0) 
                throw new ArgumentOutOfRangeException((startIndex<0 ? "startIndex" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
            if (startIndex >= _size || count > startIndex + 1)
                throw new ArgumentOutOfRangeException((startIndex>=_size ? "startIndex" : "count"), Environment.GetResourceString("ArgumentOutOfRange_BiggerThanCollection"));
            return Array.LastIndexOf((Array)_items, value, startIndex, count); 
        }
 
        // Returns a read-only IList wrapper for the given IList. 
        //
        public static IList ReadOnly(IList list) { 
            if (list==null)
                throw new ArgumentNullException("list");
            return new ReadOnlyList(list);
        } 

        // Returns a read-only ArrayList wrapper for the given ArrayList. 
        // 
        public static ArrayList ReadOnly(ArrayList list) {
            if (list==null) 
                throw new ArgumentNullException("list");
            return new ReadOnlyArrayList(list);
        }
 
        // Removes the element at the given index. The size of the list is
        // decreased by one. 
        // 
        public virtual void Remove(Object obj) {
            int index = IndexOf(obj); 
            BCLDebug.Correctness(index >= 0 || !(obj is Int32), "You passed an Int32 to Remove that wasn't in the ArrayList.\r\nDid you mean RemoveAt?  int: "+obj+"  Count: "+Count);
            if (index >=0)
                RemoveAt(index);
        } 

        // Removes the element at the given index. The size of the list is 
        // decreased by one. 
        //
        public virtual void RemoveAt(int index) { 
            if (index < 0 || index >= _size) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index"));
            _size--;
            if (index < _size) {
                Array.Copy(_items, index + 1, _items, index, _size - index); 
            }
            _items[_size] = null; 
            _version++; 
        }
 
        // Removes a range of elements from this list.
        //
        public virtual void RemoveRange(int index, int count) {
            if (index < 0 || count < 0) 
                throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
            if (_size - index < count) 
                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); 

            if (count > 0) { 
                int i = _size;
                _size -= count;
                if (index < _size) {
                    Array.Copy(_items, index + count, _items, index, _size - index); 
                }
                while (i > _size) _items[--i] = null; 
                _version++; 
            }
        } 

        // Returns an IList that contains count copies of value.
        //
        public static ArrayList Repeat(Object value, int count) { 
            if (count < 0)
                throw new ArgumentOutOfRangeException("count",Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
 
            ArrayList list = new ArrayList((count>_defaultCapacity)?count:_defaultCapacity);
            for(int i=0; i _size - count) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index")); 
 
            if (count > 0) {
                c.CopyTo(_items, index); 
                _version++;
            }
        }
 
        public virtual ArrayList GetRange(int index, int count) {
            if (index < 0 || count < 0) 
                throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
            if (_size - index < count)
                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); 
             return new Range(this,index, count);
        }

        // Sorts the elements in this list.  Uses the default comparer and 
        // Array.Sort.
        public virtual void Sort() 
        { 
            Sort(0, Count, Comparer.Default);
        } 

        // Sorts the elements in this list.  Uses Array.Sort with the
        // provided comparer.
        public virtual void Sort(IComparer comparer) 
        {
            Sort(0, Count, comparer); 
        } 

        // Sorts the elements in a section of this list. The sort compares the 
        // elements to each other using the given IComparer interface. If
        // comparer is null, the elements are compared to each other using
        // the IComparable interface, which in that case must be implemented by all
        // elements of the list. 
        //
        // This method uses the Array.Sort method to sort the elements. 
        // 
        public virtual void Sort(int index, int count, IComparer comparer) {
            if (index < 0 || count < 0) 
                throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
            if (_size - index < count)
                throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
 
            Array.Sort(_items, index, count, comparer);
            _version++; 
        } 

        // Returns a thread-safe wrapper around an IList. 
        //
        [HostProtection(Synchronization=true)]
        public static IList Synchronized(IList list) {
            if (list==null) 
                throw new ArgumentNullException("list");
            return new SyncIList(list); 
        } 

        // Returns a thread-safe wrapper around a ArrayList. 
        //
        [HostProtection(Synchronization=true)]
        public static ArrayList Synchronized(ArrayList list) {
            if (list==null) 
                throw new ArgumentNullException("list");
            return new SyncArrayList(list); 
        } 

        // ToArray returns a new Object array containing the contents of the ArrayList. 
        // This requires copying the ArrayList, which is an O(n) operation.
        public virtual Object[] ToArray() {
            Object[] array = new Object[_size];
            Array.Copy(_items, 0, array, 0, _size); 
            return array;
        } 
 
        // ToArray returns a new array of a particular type containing the contents
        // of the ArrayList.  This requires copying the ArrayList and potentially 
        // downcasting all elements.  This copy may fail and is an O(n) operation.
        // Internally, this implementation calls Array.Copy.
        //
        public virtual Array ToArray(Type type) { 
            if (type==null)
                throw new ArgumentNullException("type"); 
            Array array = Array.CreateInstance(type, _size); 
            Array.Copy(_items, 0, array, 0, _size);
            return array; 
        }

        // Sets the capacity of this list to the size of the list. This method can
        // be used to minimize a list's memory overhead once it is known that no 
        // new elements will be added to the list. To completely clear a list and
        // release all memory referenced by the list, execute the following 
        // statements: 
        //
        // list.Clear(); 
        // list.TrimToSize();
        //
        public virtual void TrimToSize() {
            Capacity = _size; 
        }
 
 
        // This class wraps an IList, exposing it as a ArrayList
        // Note this requires reimplementing half of ArrayList... 
        [Serializable()]
        private class IListWrapper : ArrayList
        {
            private IList _list; 

            internal IListWrapper(IList list) { 
                _list = list; 
                _version = 0; // list doesn't not contain a version number
            } 

             public override int Capacity {
                get { return _list.Count; }
                set { 
                    if (value < _list.Count) throw new ArgumentOutOfRangeException("value", Environment.GetResourceString("ArgumentOutOfRange_SmallCapacity"));
                } 
            } 

            public override int Count { 
                get { return _list.Count; }
            }

            public override bool IsReadOnly { 
                get { return _list.IsReadOnly; }
            } 
 
            public override bool IsFixedSize {
                get { return _list.IsFixedSize; } 
            }


            public override bool IsSynchronized { 
                get { return _list.IsSynchronized; }
            } 
 
             public override Object this[int index] {
                get { 
                    return _list[index];
                }
                set {
                    _list[index] = value; 
                    _version++;
                } 
            } 

            public override Object SyncRoot { 
                get { return _list.SyncRoot; }
            }

            public override int Add(Object obj) { 
                int i = _list.Add(obj);
                _version++; 
                return i; 
            }
 
            public override void AddRange(ICollection c) {
                InsertRange(Count, c);
            }
 
            // Other overloads with automatically work
            public override int BinarySearch(int index, int count, Object value, IComparer comparer) 
            { 
                if (index < 0 || count < 0)
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
                if (_list.Count - index < count)
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
                if (comparer == null)
                    comparer = Comparer.Default; 

                int lo = index; 
                int hi = index + count - 1; 
                int mid;
                while (lo <= hi) { 
                    mid = (lo+hi)/2;
                    int r = comparer.Compare(value, _list[mid]);
                    if (r == 0)
                        return mid; 
                    if (r < 0)
                        hi = mid-1; 
                    else 
                        lo = mid+1;
                } 
                // return bitwise complement of the first element greater than value.
                // Since hi is less than lo now, ~lo is the correct item.
                return ~lo;
            } 

            public override void Clear() { 
                // If _list is an array, it will support Clear method. 
                // We shouldn't allow clear operation on a FixedSized ArrayList
                if(_list.IsFixedSize) { 
                    throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection"));
                }

                _list.Clear(); 
                _version++;
            } 
 
            public override Object Clone() {
                // This does not do a shallow copy of _list into a ArrayList! 
                // This clones the IListWrapper, creating another wrapper class!
                return new IListWrapper(_list);
            }
 
            public override bool Contains(Object obj) {
                return _list.Contains(obj); 
            } 

            public override void CopyTo(Array array, int index) { 
                _list.CopyTo(array, index);
            }

            public override void CopyTo(int index, Array array, int arrayIndex, int count) { 
                if (array==null)
                    throw new ArgumentNullException("array"); 
                if (index < 0 || arrayIndex < 0) 
                    throw new ArgumentOutOfRangeException((index < 0) ? "index" : "arrayIndex", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
                if( count < 0) 
                    throw new ArgumentOutOfRangeException( "count" , Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
                if (array.Length - arrayIndex < count)
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
                if (_list.Count - index < count) 
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
                if (array.Rank != 1) 
                    throw new ArgumentException(Environment.GetResourceString("Arg_RankMultiDimNotSupported")); 

                for(int i=index; i _list.Count) throw new ArgumentOutOfRangeException("startIndex", Environment.GetResourceString("ArgumentOutOfRange_Index"));
                if (count < 0 || startIndex > _list.Count - count) throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_Count")); 

                int endIndex = startIndex + count;
                if (value == null) {
                    for(int i=startIndex; i _list.Count) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index")); 
 
                if( c.Count > 0) {
                    ArrayList al = _list as ArrayList; 
                    if( al != null) {
                        // We need to special case ArrayList.
                        // When c is a range of _list, we need to handle this in a special way.
                        // See ArrayList.InsertRange for details. 
                        al.InsertRange(index, c);
                    } 
                    else { 
                        IEnumerator en = c.GetEnumerator();
                        while(en.MoveNext()) { 
                            _list.Insert(index++, en.Current);
                        }
                    }
                    _version++; 
                }
            } 
 
            public override int LastIndexOf(Object value) {
                 return LastIndexOf(value,_list.Count - 1, _list.Count); 
            }

            public override int LastIndexOf(Object value, int startIndex) {
                return LastIndexOf(value, startIndex, startIndex + 1); 
            }
 
            public override int LastIndexOf(Object value, int startIndex, int count) { 
                if (_list.Count == 0)
                    return -1; 

                if (startIndex < 0 || startIndex >= _list.Count) throw new ArgumentOutOfRangeException("startIndex", Environment.GetResourceString("ArgumentOutOfRange_Index"));
                if (count < 0 || count > startIndex + 1) throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_Count"));
 
                int endIndex = startIndex - count + 1;
                if (value == null) { 
                    for(int i=startIndex; i >= endIndex; i--) 
                        if (_list[i] == null)
                            return i; 
                    return -1;
                } else {
                    for(int i=startIndex; i >= endIndex; i--)
                        if (_list[i] != null && _list[i].Equals(value)) 
                            return i;
                    return -1; 
                } 
            }
 
            public override void Remove(Object value) {
                int index = IndexOf(value);
                if (index >=0)
                    RemoveAt(index); 
            }
 
            public override void RemoveAt(int index) { 
                _list.RemoveAt(index);
                _version++; 
            }

            public override void RemoveRange(int index, int count) {
                if (index < 0 || count < 0) 
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
                if (_list.Count - index < count) 
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); 

                if( count > 0)    // be consistent with ArrayList 
                    _version++;

                while(count > 0) {
                    _list.RemoveAt(index); 
                    count--;
                } 
            } 

            public override void Reverse(int index, int count) { 
                if (index < 0 || count < 0)
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
                if (_list.Count - index < count)
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); 

                int i = index; 
                int j = index + count - 1; 
                while (i < j)
                { 
                    Object tmp = _list[i];
                    _list[i++] = _list[j];
                    _list[j--] = tmp;
                } 
                _version++;
            } 
 
            public override void SetRange(int index, ICollection c) {
                if (c==null) { 
                    throw new ArgumentNullException("c", Environment.GetResourceString("ArgumentNull_Collection"));
                }

                if (index < 0 || index > _list.Count - c.Count) { 
                    throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index"));
                } 
 
                if( c.Count > 0) {
                    IEnumerator en = c.GetEnumerator(); 
                    while(en.MoveNext()) {
                        _list[index++] = en.Current;
                    }
                    _version++; 
                }
            } 
 
            public override ArrayList GetRange(int index, int count) {
                if (index < 0 || count < 0) 
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
                if (_list.Count - index < count)
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
                 return new Range(this,index, count); 
            }
 
            public override void Sort(int index, int count, IComparer comparer) { 
                if (index < 0 || count < 0)
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
                if (_list.Count - index < count)
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));

                Object [] array = new Object[count]; 
                CopyTo(index, array, 0, count);
                Array.Sort(array, 0, count, comparer); 
                for(int i=0; i 0 && _en.MoveNext()); 
                    _remaining = count;
                    _firstCall = true;
                }
 
                public Object Clone() {
                    // We must clone the underlying enumerator, I think. 
                    IListWrapperEnumWrapper clone = new IListWrapperEnumWrapper(); 
                    clone._en = (IEnumerator) ((ICloneable)_en).Clone();
                    clone._initialStartIndex = _initialStartIndex; 
                    clone._initialCount = _initialCount;
                    clone._remaining = _remaining;
                    clone._firstCall = _firstCall;
                    return clone; 
                }
 
                public bool MoveNext() { 
                    if (_firstCall) {
                        _firstCall = false; 
                        return _remaining-- > 0 && _en.MoveNext();
                    }
                    if (_remaining < 0)
                        return false; 
                    bool r = _en.MoveNext();
                    return r && _remaining-- > 0; 
                } 

                public Object Current { 
                    get {
                        if (_firstCall)
                            throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumNotStarted));
                        if (_remaining < 0) 
                            throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumEnded));
                        return _en.Current; 
                    } 
                }
 
                public void Reset() {
                    _en.Reset();
                    int startIndex = _initialStartIndex;
                    while(startIndex-- > 0 && _en.MoveNext()); 
                    _remaining = _initialCount;
                    _firstCall = true; 
                } 
            }
        } 


        [Serializable()]
        private class SyncArrayList : ArrayList 
        {
            private ArrayList _list; 
            private Object _root; 

            internal SyncArrayList(ArrayList list) 
                : base( false )
            {
                _list = list;
                _root = list.SyncRoot; 
            }
 
            public override int Capacity { 
                get {
                    lock(_root) { 
                        return _list.Capacity;
                    }
                }
                set { 
                    lock(_root) {
                        _list.Capacity = value; 
                    } 
                }
            } 

            public override int Count {
                get { lock(_root) { return _list.Count; } }
            } 

            public override bool IsReadOnly { 
                get { return _list.IsReadOnly; } 
            }
 
            public override bool IsFixedSize {
                get { return _list.IsFixedSize; }
            }
 

            public override bool IsSynchronized { 
                get { return true; } 
            }
 
             public override Object this[int index] {
                get {
                    lock(_root) {
                        return _list[index]; 
                    }
                } 
                set { 
                    lock(_root) {
                        _list[index] = value; 
                    }
                }
            }
 
            public override Object SyncRoot {
                get { return _root; } 
            } 

            public override int Add(Object value) { 
                lock(_root) {
                    return _list.Add(value);
                }
            } 

            public override void AddRange(ICollection c) { 
                lock(_root) { 
                    _list.AddRange(c);
                } 
            }

            public override int BinarySearch(Object value) {
                lock(_root) { 
                    return _list.BinarySearch(value);
                } 
            } 

            public override int BinarySearch(Object value, IComparer comparer) { 
                lock(_root) {
                    return _list.BinarySearch(value, comparer);
                }
            } 

            public override int BinarySearch(int index, int count, Object value, IComparer comparer) { 
                lock(_root) { 
                    return _list.BinarySearch(index, count, value, comparer);
                } 
            }

            public override void Clear() {
                lock(_root) { 
                    _list.Clear();
                } 
            } 

            public override Object Clone() { 
                lock(_root) {
                    return new SyncArrayList((ArrayList)_list.Clone());
                }
            } 

            public override bool Contains(Object item) { 
                lock(_root) { 
                    return _list.Contains(item);
                } 
            }

            public override void CopyTo(Array array) {
                lock(_root) { 
                    _list.CopyTo(array);
                } 
            } 

            public override void CopyTo(Array array, int index) { 
                lock(_root) {
                    _list.CopyTo(array, index);
                }
            } 

            public override void CopyTo(int index, Array array, int arrayIndex, int count) { 
                lock(_root) { 
                    _list.CopyTo(index, array, arrayIndex, count);
                } 
            }

            public override IEnumerator GetEnumerator() {
                lock(_root) { 
                    return _list.GetEnumerator();
                } 
            } 

            public override IEnumerator GetEnumerator(int index, int count) { 
                lock(_root) {
                    return _list.GetEnumerator(index, count);
                }
            } 

            public override int IndexOf(Object value) { 
                lock(_root) { 
                    return _list.IndexOf(value);
                } 
            }

            public override int IndexOf(Object value, int startIndex) {
                lock(_root) { 
                    return _list.IndexOf(value, startIndex);
                } 
            } 

            public override int IndexOf(Object value, int startIndex, int count) { 
                lock(_root) {
                    return _list.IndexOf(value, startIndex, count);
                }
            } 

            public override void Insert(int index, Object value) { 
                lock(_root) { 
                    _list.Insert(index, value);
                } 
            }

            public override void InsertRange(int index, ICollection c) {
                lock(_root) { 
                    _list.InsertRange(index, c);
                } 
            } 

            public override int LastIndexOf(Object value) { 
                lock(_root) {
                    return _list.LastIndexOf(value);
                }
            } 

            public override int LastIndexOf(Object value, int startIndex) { 
                lock(_root) { 
                    return _list.LastIndexOf(value, startIndex);
                } 
            }

            public override int LastIndexOf(Object value, int startIndex, int count) {
                lock(_root) { 
                    return _list.LastIndexOf(value, startIndex, count);
                } 
            } 

            public override void Remove(Object value) { 
                lock(_root) {
                    _list.Remove(value);
                }
            } 

            public override void RemoveAt(int index) { 
                lock(_root) { 
                    _list.RemoveAt(index);
                } 
            }

            public override void RemoveRange(int index, int count) {
                lock(_root) { 
                    _list.RemoveRange(index, count);
                } 
            } 

            public override void Reverse(int index, int count) { 
                lock(_root) {
                    _list.Reverse(index, count);
                }
            } 

            public override void SetRange(int index, ICollection c) { 
                lock(_root) { 
                    _list.SetRange(index, c);
                } 
            }

            public override ArrayList GetRange(int index, int count) {
                lock(_root) { 
                    return _list.GetRange(index, count);
                } 
            } 

            public override void Sort() { 
                lock(_root) {
                    _list.Sort();
                }
            } 

            public override void Sort(IComparer comparer) { 
                lock(_root) { 
                    _list.Sort(comparer);
                } 
            }

            public override void Sort(int index, int count, IComparer comparer) {
                lock(_root) { 
                    _list.Sort(index, count, comparer);
                } 
            } 

            public override Object[] ToArray() { 
                lock(_root) {
                    return _list.ToArray();
                }
            } 

            public override Array ToArray(Type type) { 
                lock(_root) { 
                    return _list.ToArray(type);
                } 
            }

            public override void TrimToSize() {
                lock(_root) { 
                    _list.TrimToSize();
                } 
            } 
        }
 

        [Serializable()]
        private class SyncIList : IList
        { 
            private IList _list;
            private Object _root; 
 
            internal SyncIList(IList list) {
                _list = list; 
                _root = list.SyncRoot;
            }

            public virtual int Count { 
                get { lock(_root) { return _list.Count; } }
            } 
 
            public virtual bool IsReadOnly {
                get { return _list.IsReadOnly; } 
            }

            public virtual bool IsFixedSize {
                get { return _list.IsFixedSize; } 
            }
 
 
            public virtual bool IsSynchronized {
                get { return true; } 
            }

             public virtual Object this[int index] {
                get { 
                    lock(_root) {
                        return _list[index]; 
                    } 
                }
                set { 
                    lock(_root) {
                        _list[index] = value;
                    }
                } 
            }
 
            public virtual Object SyncRoot { 
                get { return _root; }
            } 

            public virtual int Add(Object value) {
                lock(_root) {
                    return _list.Add(value); 
                }
            } 
 

            public virtual void Clear() { 
                lock(_root) {
                    _list.Clear();
                }
            } 

            public virtual bool Contains(Object item) { 
                lock(_root) { 
                    return _list.Contains(item);
                } 
            }

            public virtual void CopyTo(Array array, int index) {
                lock(_root) { 
                    _list.CopyTo(array, index);
                } 
            } 

            public virtual IEnumerator GetEnumerator() { 
                lock(_root) {
                    return _list.GetEnumerator();
                }
            } 

            public virtual int IndexOf(Object value) { 
                lock(_root) { 
                    return _list.IndexOf(value);
                } 
            }

            public virtual void Insert(int index, Object value) {
                lock(_root) { 
                    _list.Insert(index, value);
                } 
            } 

            public virtual void Remove(Object value) { 
                lock(_root) {
                    _list.Remove(value);
                }
            } 

            public virtual void RemoveAt(int index) { 
                lock(_root) { 
                    _list.RemoveAt(index);
                } 
            }
        }

        [Serializable()] private class FixedSizeList : IList 
        {
            private IList _list; 
 
            internal FixedSizeList(IList l) {
                _list = l; 
            }

            public virtual int Count {
                get { return _list.Count; } 
            }
 
            public virtual bool IsReadOnly { 
                get { return _list.IsReadOnly; }
            } 

            public virtual bool IsFixedSize {
                get { return true; }
            } 

            public virtual bool IsSynchronized { 
                get { return _list.IsSynchronized; } 
            }
 
             public virtual Object this[int index] {
                get {
                    return _list[index];
                } 
                set {
                    _list[index] = value; 
                } 
            }
 
            public virtual Object SyncRoot {
                get { return _list.SyncRoot; }
            }
 
            public virtual int Add(Object obj) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection")); 
            } 

            public virtual void Clear() { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection"));
            }

            public virtual bool Contains(Object obj) { 
                return _list.Contains(obj);
            } 
 
            public virtual void CopyTo(Array array, int index) {
                _list.CopyTo(array, index); 
            }

            public virtual IEnumerator GetEnumerator() {
                return _list.GetEnumerator(); 
            }
 
            public virtual int IndexOf(Object value) { 
                return _list.IndexOf(value);
            } 

            public virtual void Insert(int index, Object obj) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection"));
            } 

            public virtual void Remove(Object value) { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection")); 
            }
 
            public virtual void RemoveAt(int index) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection"));
            }
        } 

        [Serializable()] private class FixedSizeArrayList : ArrayList 
        { 
            private ArrayList _list;
 
            internal FixedSizeArrayList(ArrayList l) {
                _list = l;
                _version = _list._version;
            } 

            public override int Count { 
                get { return _list.Count; } 
            }
 
            public override bool IsReadOnly {
                get { return _list.IsReadOnly; }
            }
 
            public override bool IsFixedSize {
                get { return true; } 
            } 

            public override bool IsSynchronized { 
                get { return _list.IsSynchronized; }
            }

             public override Object this[int index] { 
                get {
                    return _list[index]; 
                } 
                set {
                    _list[index] = value; 
                    _version = _list._version;
                }
            }
 
            public override Object SyncRoot {
                get { return _list.SyncRoot; } 
            } 

            public override int Add(Object obj) { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection"));
            }

            public override void AddRange(ICollection c) { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection"));
            } 
 
            public override int BinarySearch(int index, int count, Object value, IComparer comparer) {
                return _list.BinarySearch(index, count, value, comparer); 
            }

            public override int Capacity {
                get { return _list.Capacity; } 
                set { throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection")); }
            } 
 
            public override void Clear() {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection")); 
            }

            public override Object Clone() {
                FixedSizeArrayList arrayList = new FixedSizeArrayList(_list); 
                arrayList._list = (ArrayList)_list.Clone();
                return arrayList; 
            } 

            public override bool Contains(Object obj) { 
                return _list.Contains(obj);
            }

            public override void CopyTo(Array array, int index) { 
                _list.CopyTo(array, index);
            } 
 
            public override void CopyTo(int index, Array array, int arrayIndex, int count) {
                _list.CopyTo(index, array, arrayIndex, count); 
            }

            public override IEnumerator GetEnumerator() {
                return _list.GetEnumerator(); 
            }
 
            public override IEnumerator GetEnumerator(int index, int count) { 
                return _list.GetEnumerator(index, count);
            } 

            public override int IndexOf(Object value) {
                return _list.IndexOf(value);
            } 

            public override int IndexOf(Object value, int startIndex) { 
                return _list.IndexOf(value, startIndex); 
            }
 
            public override int IndexOf(Object value, int startIndex, int count) {
                return _list.IndexOf(value, startIndex, count);
            }
 
            public override void Insert(int index, Object obj) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection")); 
            } 

            public override void InsertRange(int index, ICollection c) { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection"));
            }

            public override int LastIndexOf(Object value) { 
                return _list.LastIndexOf(value);
            } 
 
            public override int LastIndexOf(Object value, int startIndex) {
                return _list.LastIndexOf(value, startIndex); 
            }

            public override int LastIndexOf(Object value, int startIndex, int count) {
                return _list.LastIndexOf(value, startIndex, count); 
            }
 
            public override void Remove(Object value) { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection"));
            } 

            public override void RemoveAt(int index) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection"));
            } 

            public override void RemoveRange(int index, int count) { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection")); 
            }
 
            public override void SetRange(int index, ICollection c) {
                _list.SetRange(index, c);
                _version = _list._version;
            } 

            public override ArrayList GetRange(int index, int count) { 
                if (index < 0 || count < 0) 
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
                if (Count - index < count) 
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
                 return new Range(this,index, count);
            }
 
            public override void Reverse(int index, int count) {
                _list.Reverse(index, count); 
                _version = _list._version; 
            }
 
            public override void Sort(int index, int count, IComparer comparer) {
                _list.Sort(index, count, comparer);
                _version = _list._version;
            } 

            public override Object[] ToArray() { 
                return _list.ToArray(); 
            }
 
            public override Array ToArray(Type type) {
                return _list.ToArray(type);
            }
 
            public override void TrimToSize() {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_FixedSizeCollection")); 
            } 
        }
 
        [Serializable()] private class ReadOnlyList : IList
        {
            private IList _list;
 
            internal ReadOnlyList(IList l) {
                _list = l; 
            } 

            public virtual int Count { 
                get { return _list.Count; }
            }

            public virtual bool IsReadOnly { 
                get { return true; }
            } 
 
            public virtual bool IsFixedSize {
                get { return true; } 
            }

            public virtual bool IsSynchronized {
                get { return _list.IsSynchronized; } 
            }
 
             public virtual Object this[int index] { 
                get {
                    return _list[index]; 
                }
                set {
                    throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection"));
                } 
            }
 
            public virtual Object SyncRoot { 
                get { return _list.SyncRoot; }
            } 

            public virtual int Add(Object obj) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection"));
            } 

            public virtual void Clear() { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection")); 
            }
 
            public virtual bool Contains(Object obj) {
                return _list.Contains(obj);
            }
 
            public virtual void CopyTo(Array array, int index) {
                _list.CopyTo(array, index); 
            } 

            public virtual IEnumerator GetEnumerator() { 
                return _list.GetEnumerator();
            }

            public virtual int IndexOf(Object value) { 
                return _list.IndexOf(value);
            } 
 
            public virtual void Insert(int index, Object obj) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection")); 
            }

            public virtual void Remove(Object value) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection")); 
            }
 
            public virtual void RemoveAt(int index) { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection"));
            } 
        }

        [Serializable()] private class ReadOnlyArrayList : ArrayList
        { 
            private ArrayList _list;
 
            internal ReadOnlyArrayList(ArrayList l) { 
                _list = l;
            } 

            public override int Count {
                get { return _list.Count; }
            } 

            public override bool IsReadOnly { 
                get { return true; } 
            }
 
            public override bool IsFixedSize {
                get { return true; }
            }
 
            public override bool IsSynchronized {
                get { return _list.IsSynchronized; } 
            } 

             public override Object this[int index] { 
                get {
                    return _list[index];
                }
                set { 
                    throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection"));
                } 
            } 

            public override Object SyncRoot { 
                get { return _list.SyncRoot; }
            }

            public override int Add(Object obj) { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection"));
            } 
 
            public override void AddRange(ICollection c) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection")); 
            }

            public override int BinarySearch(int index, int count, Object value, IComparer comparer) {
                return _list.BinarySearch(index, count, value, comparer); 
            }
 
 
            public override int Capacity {
                get { return _list.Capacity; } 
                set { throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection")); }
            }

            public override void Clear() { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection"));
            } 
 
            public override Object Clone() {
                ReadOnlyArrayList arrayList = new ReadOnlyArrayList(_list); 
                arrayList._list = (ArrayList)_list.Clone();
                return arrayList;
            }
 
            public override bool Contains(Object obj) {
                return _list.Contains(obj); 
            } 

            public override void CopyTo(Array array, int index) { 
                _list.CopyTo(array, index);
            }

            public override void CopyTo(int index, Array array, int arrayIndex, int count) { 
                _list.CopyTo(index, array, arrayIndex, count);
            } 
 
            public override IEnumerator GetEnumerator() {
                return _list.GetEnumerator(); 
            }

            public override IEnumerator GetEnumerator(int index, int count) {
                return _list.GetEnumerator(index, count); 
            }
 
            public override int IndexOf(Object value) { 
                return _list.IndexOf(value);
            } 

            public override int IndexOf(Object value, int startIndex) {
                return _list.IndexOf(value, startIndex);
            } 

            public override int IndexOf(Object value, int startIndex, int count) { 
                return _list.IndexOf(value, startIndex, count); 
            }
 
            public override void Insert(int index, Object obj) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection"));
            }
 
            public override void InsertRange(int index, ICollection c) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection")); 
            } 

            public override int LastIndexOf(Object value) { 
                return _list.LastIndexOf(value);
            }

            public override int LastIndexOf(Object value, int startIndex) { 
                return _list.LastIndexOf(value, startIndex);
            } 
 
            public override int LastIndexOf(Object value, int startIndex, int count) {
                return _list.LastIndexOf(value, startIndex, count); 
            }

            public override void Remove(Object value) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection")); 
            }
 
            public override void RemoveAt(int index) { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection"));
            } 

            public override void RemoveRange(int index, int count) {
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection"));
            } 

            public override void SetRange(int index, ICollection c) { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection")); 
            }
 
            public override ArrayList GetRange(int index, int count) {
                if (index < 0 || count < 0)
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
                if (Count - index < count) 
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
                 return new Range(this,index, count); 
            } 

            public override void Reverse(int index, int count) { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection"));
            }

            public override void Sort(int index, int count, IComparer comparer) { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection"));
            } 
 
            public override Object[] ToArray() {
                return _list.ToArray(); 
            }

            public override Array ToArray(Type type) {
                return _list.ToArray(type); 
            }
 
            public override void TrimToSize() { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_ReadOnlyCollection"));
            } 
        }


        // Implements an enumerator for a ArrayList. The enumerator uses the 
        // internal version number of the list to ensure that no modifications are
        // made to the list while an enumeration is in progress. 
        [Serializable()] private sealed class ArrayListEnumerator : IEnumerator, ICloneable 
        {
            private ArrayList list; 
            private int index;
            private int endIndex;       // Where to stop.
            private int version;
            private Object currentElement; 
            private int startIndex;     // Save this for Reset.
 
            internal ArrayListEnumerator(ArrayList list, int index, int count) { 
                this.list = list;
                startIndex = index; 
                this.index = index - 1;
                endIndex = this.index + count;  // last valid index
                version = list._version;
                currentElement = null; 
            }
 
            public Object Clone() { 
                return MemberwiseClone();
            } 

            public bool MoveNext() {
                if (version != list._version) throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumFailedVersion));
                if (index < endIndex) { 
                    currentElement = list[++index];
                    return true; 
                } 
                else {
                    index = endIndex + 1; 
                }

                return false;
            } 

            public Object Current { 
                get { 
                    if (index < startIndex)
                        throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumNotStarted)); 
                    else if (index > endIndex) {
                        throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumEnded));
                    }
                    return currentElement; 
                }
            } 
 
            public void Reset() {
                if (version != list._version) throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumFailedVersion)); 
                index = startIndex - 1;
            }
        }
 
        // Implementation of a generic list subrange. An instance of this class
        // is returned by the default implementation of List.GetRange. 
        [Serializable()] 
        private class Range: ArrayList
        { 
            private ArrayList _baseList;
            private int _baseIndex;
            private int _baseSize;
            private int _baseVersion; 

            internal Range(ArrayList list, int index, int count) : base(false) { 
                _baseList = list; 
                _baseIndex = index;
                _baseSize = count; 
                _baseVersion = list._version;
                // we also need to update _version field to make Range of Range work
                _version = list._version;
            } 

            private void InternalUpdateRange() 
            { 
                if (_baseVersion != _baseList._version)
                    throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_UnderlyingArrayListChanged")); 
            }

            private void InternalUpdateVersion() {
                _baseVersion++; 
                _version++;
            } 
 
            public override int Add(Object value) {
                InternalUpdateRange(); 
                _baseList.Insert(_baseIndex + _baseSize, value);
                InternalUpdateVersion();
                return _baseSize++;
            } 

            public override void AddRange(ICollection c) { 
                InternalUpdateRange(); 
                if( c ==  null ) {
                    throw new ArgumentNullException("c"); 
                }

                int count = c.Count;
                if( count > 0) { 
                    _baseList.InsertRange(_baseIndex + _baseSize, c);
                    InternalUpdateVersion(); 
                    _baseSize += count; 
                }
            } 

            // Other overloads with automatically work
            public override int BinarySearch(int index, int count, Object value, IComparer comparer) {
                InternalUpdateRange(); 
                if (index < 0 || count < 0)
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
                if (_baseSize - index < count) 
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
                int i = _baseList.BinarySearch(_baseIndex + index, count, value, comparer); 
                if (i >= 0) return i - _baseIndex;
                return i + _baseIndex;
            }
 
            public override int Capacity {
                get { 
                    return _baseList.Capacity; 
                }
 
                set {
                     if (value < Count) throw new ArgumentOutOfRangeException("value", Environment.GetResourceString("ArgumentOutOfRange_SmallCapacity"));
                }
            } 

 
            public override void Clear() { 
                InternalUpdateRange();
                if (_baseSize != 0) 
                {
                    _baseList.RemoveRange(_baseIndex, _baseSize);
                    InternalUpdateVersion();
                    _baseSize = 0; 
                }
            } 
 
            public override Object Clone() {
                InternalUpdateRange(); 
                Range arrayList = new Range(_baseList,_baseIndex,_baseSize);
                arrayList._baseList = (ArrayList)_baseList.Clone();
                return arrayList;
            } 

            public override bool Contains(Object item) { 
              InternalUpdateRange(); 
              if (item==null) {
                    for(int i=0; i<_baseSize; i++) 
                        if (_baseList[_baseIndex + i]==null)
                            return true;
                    return false;
                } 
                else {
                    for(int i=0; i<_baseSize; i++) 
                        if (_baseList[_baseIndex + i] != null && _baseList[_baseIndex + i].Equals(item)) 
                            return true;
                    return false; 
                }
            }

            public override void CopyTo(Array array, int index) { 
                InternalUpdateRange();
                if (array==null) 
                    throw new ArgumentNullException("array"); 
                if (array.Rank != 1)
                    throw new ArgumentException(Environment.GetResourceString("Arg_RankMultiDimNotSupported")); 
                if (index < 0)
                    throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
                if (array.Length - index < _baseSize)
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); 
                _baseList.CopyTo(_baseIndex, array, index, _baseSize);
             } 
 
            public override void CopyTo(int index, Array array, int arrayIndex, int count) {
                InternalUpdateRange(); 
                if (array==null)
                    throw new ArgumentNullException("array");
                if (array.Rank != 1)
                    throw new ArgumentException(Environment.GetResourceString("Arg_RankMultiDimNotSupported")); 
                if (index < 0 || count < 0)
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
                if (array.Length - arrayIndex < count) 
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
                if (_baseSize - index < count) 
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
                _baseList.CopyTo(_baseIndex + index, array, arrayIndex, count);
            }
 
            public override int Count {
                get { 
                 InternalUpdateRange(); 
                 return _baseSize;
                } 
            }

            public override bool IsReadOnly {
                get { return _baseList.IsReadOnly; } 
            }
 
            public override bool IsFixedSize { 
                get { return _baseList.IsFixedSize; }
            } 

            public override bool IsSynchronized {
                get { return _baseList.IsSynchronized; }
            } 

            public override IEnumerator GetEnumerator() { 
                return GetEnumerator(0,_baseSize); 
            }
 
            public override IEnumerator GetEnumerator(int index, int count) {
                InternalUpdateRange();
                if (index < 0 || count < 0)
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
                if (_baseSize - index < count)
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); 
                return _baseList.GetEnumerator(_baseIndex + index, count); 
            }
 
            public override ArrayList GetRange(int index, int count) {
                InternalUpdateRange();
                if (index < 0 || count < 0)
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
                if (_baseSize - index < count)
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); 
                return new Range(this, index, count); 
            }
 
            public override Object SyncRoot {
                get {
                    return _baseList.SyncRoot;
                } 
            }
 
 
            public override int IndexOf(Object value) {
                InternalUpdateRange(); 
                int i = _baseList.IndexOf(value, _baseIndex, _baseSize);
                if (i >= 0) return i - _baseIndex;
                return -1;
            } 

            public override int IndexOf(Object value, int startIndex) { 
                InternalUpdateRange(); 
                if (startIndex < 0)
                    throw new ArgumentOutOfRangeException("startIndex", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
                if (startIndex > _baseSize)
                    throw new ArgumentOutOfRangeException("startIndex", Environment.GetResourceString("ArgumentOutOfRange_Index"));

                int i = _baseList.IndexOf(value, _baseIndex + startIndex, _baseSize - startIndex); 
                if (i >= 0) return i - _baseIndex;
                return -1; 
            } 

            public override int IndexOf(Object value, int startIndex, int count) { 
                InternalUpdateRange();
                if (startIndex < 0 || startIndex > _baseSize)
                    throw new ArgumentOutOfRangeException("startIndex", Environment.GetResourceString("ArgumentOutOfRange_Index"));
 
                if (count < 0 || (startIndex > _baseSize - count))
                    throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_Count")); 
 
                int i = _baseList.IndexOf(value, _baseIndex + startIndex, count);
                if (i >= 0) return i - _baseIndex; 
                return -1;
            }

            public override void Insert(int index, Object value) { 
                InternalUpdateRange();
                if (index < 0 || index > _baseSize) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index")); 
                _baseList.Insert(_baseIndex + index, value); 
                InternalUpdateVersion();
                _baseSize++; 
            }

            public override void InsertRange(int index, ICollection c) {
                InternalUpdateRange(); 
                if (index < 0 || index > _baseSize) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index"));
 
                if( c == null) { 
                    throw new ArgumentNullException("c");
 
                }
                int count = c.Count;
                if( count > 0) {
                    _baseList.InsertRange(_baseIndex + index, c); 
                    _baseSize += count;
                    InternalUpdateVersion(); 
                } 
            }
 
            public override int LastIndexOf(Object value) {
                InternalUpdateRange();
                int i = _baseList.LastIndexOf(value, _baseIndex + _baseSize - 1, _baseSize);
                if (i >= 0) return i - _baseIndex; 
                return -1;
            } 
 
            public override int LastIndexOf(Object value, int startIndex) {
                return LastIndexOf(value, startIndex, startIndex + 1); 
            }

            public override int LastIndexOf(Object value, int startIndex, int count) {
                InternalUpdateRange(); 
                if (_baseSize == 0)
                    return -1; 
 
                if (startIndex >= _baseSize)
                    throw new ArgumentOutOfRangeException("startIndex", Environment.GetResourceString("ArgumentOutOfRange_Index")); 
                if (startIndex < 0)
                    throw new ArgumentOutOfRangeException("startIndex", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));

                int i = _baseList.LastIndexOf(value, _baseIndex + startIndex, count); 
                if (i >= 0) return i - _baseIndex;
                return -1; 
            } 

            // Don't need to override Remove 

            public override void RemoveAt(int index) {
                InternalUpdateRange();
                if (index < 0 || index >= _baseSize) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index")); 
                _baseList.RemoveAt(_baseIndex + index);
                InternalUpdateVersion(); 
                _baseSize--; 
            }
 
            public override void RemoveRange(int index, int count) {
                InternalUpdateRange();
                if (index < 0 || count < 0)
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
                if (_baseSize - index < count)
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); 
                // No need to call _bastList.RemoveRange if count is 0. 
                // In addition, _baseList won't change the vresion number if count is 0.
                if( count > 0) { 
                    _baseList.RemoveRange(_baseIndex + index, count);
                    InternalUpdateVersion();
                    _baseSize -= count;
                } 
            }
 
            public override void Reverse(int index, int count) { 
                InternalUpdateRange();
                if (index < 0 || count < 0) 
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
                if (_baseSize - index < count)
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
                _baseList.Reverse(_baseIndex + index, count); 
                InternalUpdateVersion();
            } 
 

            public override void SetRange(int index, ICollection c) { 
                InternalUpdateRange();
                if (index < 0 || index >= _baseSize) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index"));
                _baseList.SetRange(_baseIndex + index, c);
                if( c.Count > 0) { 
                    InternalUpdateVersion();
                } 
            } 

            public override void Sort(int index, int count, IComparer comparer) { 
                InternalUpdateRange();
                if (index < 0 || count < 0)
                    throw new ArgumentOutOfRangeException((index<0 ? "index" : "count"), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
                if (_baseSize - index < count) 
                    throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen"));
                _baseList.Sort(_baseIndex + index, count, comparer); 
                InternalUpdateVersion(); 
            }
 
            public override Object this[int index] {
                get {
                    InternalUpdateRange();
                    if (index < 0 || index >= _baseSize) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index")); 
                        return _baseList[_baseIndex + index];
                } 
                set { 
                    InternalUpdateRange();
                    if (index < 0 || index >= _baseSize) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_Index")); 
                    _baseList[_baseIndex + index] = value;
                    InternalUpdateVersion();
                }
            } 

            public override Object[] ToArray() { 
                InternalUpdateRange(); 
                Object[] array = new Object[_baseSize];
                Array.Copy(_baseList._items, _baseIndex, array, 0, _baseSize); 
                return array;
            }

            public override Array ToArray(Type type) { 
                InternalUpdateRange();
                if (type==null) 
                    throw new ArgumentNullException("type"); 
                Array array = Array.CreateInstance(type, _baseSize);
                _baseList.CopyTo(_baseIndex, array, 0, _baseSize); 
                return array;
            }

            public override void TrimToSize() { 
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_RangeCollection"));
            } 
        } 

        [Serializable()] private sealed class ArrayListEnumeratorSimple : IEnumerator, ICloneable { 
            private ArrayList list;
            private int index;
            private int version;
            private Object currentElement; 
            [NonSerializedAttribute]
            private bool isArrayList; 
            // this object is used to indicate enumeration has not started or has terminated 
            static Object dummyObject = new Object();
 
            internal ArrayListEnumeratorSimple(ArrayList list) {
                this.list = list;
                this.index = -1;
                version = list._version; 
                isArrayList = (list.GetType() == typeof(ArrayList));
                currentElement = dummyObject; 
            } 

            public Object Clone() { 
                return MemberwiseClone();
            }

            public bool MoveNext() { 
                if (version != list._version) {
                    throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumFailedVersion)); 
                } 

                if( isArrayList) {  // avoid calling virtual methods if we are operating on ArrayList to improve performance 
                    if (index < list._size - 1) {
                        currentElement = list._items[++index];
                        return true;
                    } 
                    else {
                        currentElement = dummyObject; 
                        index =list._size; 
                        return false;
                    } 
                }
                else {
                    if (index < list.Count - 1) {
                        currentElement = list[++index]; 
                        return true;
                    } 
                    else { 
                        index = list.Count;
                        currentElement = dummyObject; 
                        return false;
                    }
                }
            } 

            public Object Current { 
                get { 
                    object temp = currentElement;
                    if(dummyObject == temp) { // check if enumeration has not started or has terminated 
                        if (index == -1) {
                            throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumNotStarted));
                        }
                        else { 
                            throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumEnded));
                        } 
                    } 

                    return temp; 
                }
            }

            public void Reset() { 
                if (version != list._version) {
                    throw new InvalidOperationException(Environment.GetResourceString(ResId.InvalidOperation_EnumFailedVersion)); 
                } 

                currentElement = dummyObject; 
                index = -1;
            }
        }
 
        internal class ArrayListDebugView {
            private ArrayList arrayList; 
 
            public ArrayListDebugView( ArrayList arrayList) {
                if( arrayList == null) 
                    throw new ArgumentNullException("arrayList");

                this.arrayList = arrayList;
            } 

            [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)] 
            public Object[] Items { 
                get {
                    return arrayList.ToArray(); 
                }
            }
        }
    } 
}
                        

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