List.cs source code in C# .NET

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Code:

/ Dotnetfx_Win7_3.5.1 / Dotnetfx_Win7_3.5.1 / 3.5.1 / DEVDIV / depot / DevDiv / releases / whidbey / NetFXspW7 / ndp / clr / src / BCL / System / Collections / Generic / List.cs / 1 / List.cs

                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
/*============================================================
** 
** Class:  List 
**
** Purpose: Implements a generic, dynamically sized list as an 
**          array.
**
**
===========================================================*/ 
namespace System.Collections.Generic {
 
    using System; 
    using System.Diagnostics;
    using System.Collections.ObjectModel; 
    using System.Security.Permissions;

    // Implements a variable-size List that uses an array of objects to store the
    // elements. A List has a capacity, which is the allocated length 
    // of the internal array. As elements are added to a List, the capacity
    // of the List is automatically increased as required by reallocating the 
    // internal array. 
    //
    [DebuggerTypeProxy(typeof(Mscorlib_CollectionDebugView<>))] 
    [DebuggerDisplay("Count = {Count}")]
    [Serializable()]

    public class List : IList, System.Collections.IList 
    {
        private const int _defaultCapacity = 4; 
 
        private T[] _items;
        private int _size; 
        private int _version;
        [NonSerialized]
        private Object _syncRoot;
 
        static T[]  _emptyArray = new T[0];
 
        // Constructs a List. The list is initially empty and has a capacity 
        // of zero. Upon adding the first element to the list the capacity is
        // increased to 16, and then increased in multiples of two as required. 
        public List() {
            _items = _emptyArray;
        }
 
        // Constructs a List 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 List(int capacity) { 
            if (capacity < 0) ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.capacity, ExceptionResource.ArgumentOutOfRange_SmallCapacity);
            _items = new T[capacity];
        }
 
        // Constructs a List, 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 List(IEnumerable collection) { 
            if (collection==null)
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection);

            ICollection c = collection as ICollection; 
            if( c != null) {
                int count = c.Count; 
                _items = new T[count]; 
                c.CopyTo(_items, 0);
                _size = count; 
            }
            else {
                _size = 0;
                _items = new T[_defaultCapacity]; 

                using(IEnumerator en = collection.GetEnumerator()) { 
                    while(en.MoveNext()) { 
                        Add(en.Current);
                    } 
                }
            }
        }
 
        // 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 int Capacity { 
            get { return _items.Length; }
            set {
                if (value != _items.Length) {
                    if (value < _size) { 
                        ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value, ExceptionResource.ArgumentOutOfRange_SmallCapacity);
                    } 
 
                    if (value > 0) {
                        T[] newItems = new T[value]; 
                        if (_size > 0) {
                            Array.Copy(_items, 0, newItems, 0, _size);
                        }
                        _items = newItems; 
                    }
                    else { 
                        _items = _emptyArray; 
                    }
                } 
            }
        }

        // Read-only property describing how many elements are in the List. 
        public int Count {
            get { return _size; } 
        } 

        bool System.Collections.IList.IsFixedSize { 
            get { return false; }
        }

 
        // Is this List read-only?
        bool ICollection.IsReadOnly { 
            get { return false; } 
        }
 
        bool System.Collections.IList.IsReadOnly {
            get { return false; }
        }
 
        // Is this List synchronized (thread-safe)?
        bool System.Collections.ICollection.IsSynchronized { 
            get { return false; } 
        }
 
        // Synchronization root for this object.
        Object System.Collections.ICollection.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 T this[int index] {
            get { 
                // Fllowing trick can reduce the range check by one
                if ((uint) index >= (uint)_size) { 
                    ThrowHelper.ThrowArgumentOutOfRangeException(); 
                }
                return _items[index]; 
            }
            set {
                if ((uint) index >= (uint)_size) {
                    ThrowHelper.ThrowArgumentOutOfRangeException(); 
                }
                _items[index] = value; 
                _version++; 
            }
        } 

        private static bool IsCompatibleObject(object value) {
            if( (value is T) || ( value == null && !typeof(T).IsValueType) ) {
                return true; 
            }
            return false; 
        } 

        private static void VerifyValueType(object value) { 
            if( !IsCompatibleObject(value)) {
                ThrowHelper.ThrowWrongValueTypeArgumentException(value, typeof(T));
            }
        } 

        Object System.Collections.IList.this[int index] { 
            get { 
                return this[index];
            } 
            set {
                VerifyValueType(value);
                this[index] = (T) value;
            } 
        }
 
        // 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 void Add(T item) {
            if (_size == _items.Length) EnsureCapacity(_size + 1);
            _items[_size++] = item; 
            _version++;
        } 
 
        int System.Collections.IList.Add(Object item)
        { 
            VerifyValueType(item);
            Add((T) item);
            return Count - 1;
        } 

 
        // 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 void AddRange(IEnumerable collection) {
            InsertRange(_size, collection);
        } 

        public ReadOnlyCollection AsReadOnly() { 
            return new ReadOnlyCollection(this); 
        }
 
        // 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 int BinarySearch(int index, int count, T item, IComparer comparer) {
            if (index < 0 || count < 0) 
                ThrowHelper.ThrowArgumentOutOfRangeException( (index<0 ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
            if (_size - index < count) 
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen); 

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

        public int BinarySearch(T item)
        { 
            return BinarySearch(0,Count,item, null);
        } 
 
        public int BinarySearch(T item, IComparer comparer)
        { 
            return BinarySearch(0,Count,item,comparer);
        }

 
        // Clears the contents of List.
        public void Clear() { 
            if (_size > 0) 
            {
                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++;
        } 

        // Contains returns true if the specified element is in the List. 
        // It does a linear, O(n) search.  Equality is determined by calling 
        // item.Equals().
        // 
        public bool Contains(T item) {
            if ((Object) item == null) {
                for(int i=0; i<_size; i++)
                    if ((Object) _items[i] == null) 
                        return true;
                return false; 
            } 
            else {
                EqualityComparer c = EqualityComparer.Default; 
                for(int i=0; i<_size; i++) {
                    if (c.Equals(_items[i], item)) return true;
                }
                return false; 
            }
        } 
 
        bool System.Collections.IList.Contains(Object item)
        { 
            if(IsCompatibleObject(item)) {
                return Contains((T) item);
            }
            return false; 
        }
 
        public List ConvertAll(Converter converter) { 
            if( converter == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.converter); 
            }

            List list = new List(_size);
            for( int i = 0; i< _size; i++) { 
                list._items[i] = converter(_items[i]);
            } 
            list._size = _size; 
            return list;
        } 

        // Copies this List into array, which must be of a
        // compatible array type.
        // 
        public void CopyTo(T[] array) {
            CopyTo(array, 0); 
        } 

        // Copies this List into array, which must be of a 
        // compatible array type.
        //
        void System.Collections.ICollection.CopyTo(Array array, int arrayIndex) {
            if ((array != null) && (array.Rank != 1)) { 
                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
            } 
 
            try {
                // Array.Copy will check for NULL. 
                Array.Copy(_items, 0, array, arrayIndex, _size);
            }
            catch(ArrayTypeMismatchException){
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArrayType); 
            }
        } 
 
        // 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 void CopyTo(int index, T[] array, int arrayIndex, int count) {
            if (_size - index < count) { 
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
            } 
 
            // Delegate rest of error checking to Array.Copy.
            Array.Copy(_items, index, array, arrayIndex, count); 
        }

        public void CopyTo(T[] array, int arrayIndex) {
            // Delegate rest of error checking to Array.Copy. 
            Array.Copy(_items, 0, array, arrayIndex, _size);
        } 
 
        // 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; 
            }
        } 

        public bool Exists(Predicate match) {
            return FindIndex(match) != -1;
        } 

        public T Find(Predicate match) { 
            if( match == null) { 
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
            } 

            for(int i = 0 ; i < _size; i++) {
                if(match(_items[i])) {
                    return _items[i]; 
                }
            } 
            return default(T); 
        }
 
        public List FindAll(Predicate match) {
            if( match == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
            } 

            List list = new List(); 
            for(int i = 0 ; i < _size; i++) { 
                if(match(_items[i])) {
                    list.Add(_items[i]); 
                }
            }
            return list;
        } 

        public int FindIndex(Predicate match) { 
            return FindIndex(0, _size, match); 
        }
 
        public int FindIndex(int startIndex, Predicate match) {
           return FindIndex( startIndex, _size - startIndex, match);
        }
 
        public int FindIndex(int startIndex, int count, Predicate match) {
            if( (uint)startIndex > (uint)_size ) { 
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index); 
            }
 
            if (count < 0 || startIndex > _size - count) {
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_Count);
            }
 
            if( match == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match); 
            } 

            int endIndex = startIndex + count; 
            for( int i = startIndex; i < endIndex; i++) {
                if( match(_items[i])) return i;
            }
            return -1; 
        }
 
        public T FindLast(Predicate match) { 
            if( match == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match); 
            }

            for(int i = _size - 1 ; i >= 0; i--) {
                if(match(_items[i])) { 
                    return _items[i];
                } 
            } 
            return default(T);
        } 

        public int FindLastIndex(Predicate match) {
            return FindLastIndex( _size - 1, _size, match);
        } 

        public int FindLastIndex(int startIndex, Predicate match) { 
           return FindLastIndex( startIndex, startIndex + 1, match); 
        }
 
        public int FindLastIndex(int startIndex, int count, Predicate match) {
            if( match == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
            } 

            if(_size == 0) { 
                // Special case for 0 length List 
                if( startIndex != -1) {
                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index); 
                }
            }
            else {
                // Make sure we're not out of range 
                if ( (uint)startIndex >= (uint)_size) {
                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index); 
                } 
            }
 
            // 2nd have of this also catches when startIndex == MAXINT, so MAXINT - 0 + 1 == -1, which is < 0.
            if (count < 0 || startIndex - count + 1 < 0) {
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_Count);
            } 

            int endIndex = startIndex - count; 
            for( int i = startIndex; i > endIndex; i--) { 
                if( match(_items[i])) {
                    return i; 
                }
            }
            return -1;
        } 

 
        public void ForEach(Action action) { 
            if( action == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match); 
            }

            for(int i = 0 ; i < _size; i++) {
                action(_items[i]); 
            }
        } 
 
        // 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 Enumerator GetEnumerator() { 
            return new Enumerator(this);
        } 
 
        /// 
        IEnumerator IEnumerable.GetEnumerator() { 
            return new Enumerator(this);
        }

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { 
            return new Enumerator(this);
        } 
 
        public List GetRange(int index, int count) {
            if (index < 0 || count < 0) { 
                ThrowHelper.ThrowArgumentOutOfRangeException( (index<0 ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
            }

            if (_size - index < count) { 
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
            } 
 
            List list = new List(count);
            Array.Copy(_items, index, list._items, 0, count); 
            list._size = count;
            return list;
        }
 

        // 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 int IndexOf(T item) {
            return Array.IndexOf(_items, item, 0, _size); 
        } 

        int System.Collections.IList.IndexOf(Object item) 
        {
            if(IsCompatibleObject(item)) {
                return IndexOf((T)item);
            } 
            return -1;
        } 
 
        // 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 
        // index 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 int IndexOf(T item, int index) {
            if (index > _size) 
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_Index);
            return Array.IndexOf(_items, item, index, _size - index);
        }
 
        // 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 
        // index 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 int IndexOf(T item, int index, int count) {
            if (index > _size) 
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_Index); 

            if (count <0 || index > _size - count) ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_Count); 

            return Array.IndexOf(_items, item, index, 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 void Insert(int index, T item) { 
            // Note that insertions at the end are legal.
            if ((uint) index > (uint)_size) {
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_ListInsert);
            } 
            if (_size == _items.Length) EnsureCapacity(_size + 1);
            if (index < _size) { 
                Array.Copy(_items, index, _items, index + 1, _size - index); 
            }
            _items[index] = item; 
            _size++;
            _version++;
        }
 
        void System.Collections.IList.Insert(int index, Object item)
        { 
            VerifyValueType(item); 
            Insert(index, (T) item);
        } 

        // 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 List's size.
        // 
        public void InsertRange(int index, IEnumerable collection) { 
            if (collection==null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection); 
            }

            if ((uint)index > (uint)_size) {
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_Index); 
            }
 
            ICollection c = collection as ICollection; 
            if( c != null ) {    // if collection is ICollection
                int count = c.Count; 
                if (count > 0) {
                    EnsureCapacity(_size + count);
                    if (index < _size) {
                        Array.Copy(_items, index, _items, index + count, _size - index); 
                    }
 
                    // If we're inserting a List into itself, we want to be able to deal with that. 
                    if (this == c) {
                        // Copy first part of _items to insert location 
                        Array.Copy(_items, 0, _items, index, index);
                        // Copy last part of _items back to inserted location
                        Array.Copy(_items, index+count, _items, index*2, _size-index);
                    } 
                    else {
                        T[] itemsToInsert = new T[count]; 
                        c.CopyTo(itemsToInsert, 0); 
                        itemsToInsert.CopyTo(_items, index);
                    } 
                    _size += count;
                }
            }
            else { 
                using(IEnumerator en = collection.GetEnumerator()) {
                    while(en.MoveNext()) { 
                        Insert(index++, en.Current); 
                    }
                } 
            }
            _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 int LastIndexOf(T item) 
        {
            return LastIndexOf(item, _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
        // index 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 int LastIndexOf(T item, int index) 
        {
            if (index >= _size)
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_Index);
            return LastIndexOf(item, index, index + 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
        // index 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 int LastIndexOf(T item, int index, int count) { 
            if (_size == 0) {
                return -1; 
            }

            if (index < 0 || count < 0) {
                ThrowHelper.ThrowArgumentOutOfRangeException( (index<0 ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_NeedNonNegNum); 
            }
 
            if (index >= _size || count > index + 1) { 
                ThrowHelper.ThrowArgumentOutOfRangeException((index >= _size ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_BiggerThanCollection);
            } 

            return Array.LastIndexOf(_items, item, index, count);
        }
 
        // Removes the element at the given index. The size of the list is
        // decreased by one. 
        // 
        public bool Remove(T item) {
            int index = IndexOf(item); 
            if (index >= 0) {
                RemoveAt(index);
                return true;
            } 

            return false; 
        } 

        void System.Collections.IList.Remove(Object item) 
        {
            if(IsCompatibleObject(item)) {
                Remove((T) item);
            } 
        }
 
        // This method removes all items which matches the predicate. 
        // The complexity is O(n).
        public int RemoveAll(Predicate match) { 
            if( match == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
            }
 
            int freeIndex = 0;   // the first free slot in items array
 
            // Find the first item which needs to be removed. 
            while( freeIndex < _size && !match(_items[freeIndex])) freeIndex++;
            if( freeIndex >= _size) return 0; 

            int current = freeIndex + 1;
            while( current < _size) {
                // Find the first item which needs to be kept. 
                while( current < _size && match(_items[current])) current++;
 
                if( current < _size) { 
                    // copy item to the free slot.
                    _items[freeIndex++] = _items[current++]; 
                }
            }

            Array.Clear(_items, freeIndex, _size - freeIndex); 
            int result = _size - freeIndex;
            _size = freeIndex; 
            _version++; 
            return result;
        } 

        // Removes the element at the given index. The size of the list is
        // decreased by one.
        // 
        public void RemoveAt(int index) {
            if ((uint)index >= (uint)_size) { 
                ThrowHelper.ThrowArgumentOutOfRangeException(); 
            }
            _size--; 
            if (index < _size) {
                Array.Copy(_items, index + 1, _items, index, _size - index);
            }
            _items[_size] = default(T); 
            _version++;
        } 
 
        // Removes a range of elements from this list.
        // 
        public void RemoveRange(int index, int count) {
            if (index < 0 || count < 0) {
                ThrowHelper.ThrowArgumentOutOfRangeException( (index<0 ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
            } 

            if (_size - index < count) 
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen); 

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

        // Reverses the elements in this list.
        public void Reverse() {
            Reverse(0, Count); 
        }
 
        // Reverses the elements in a range of this list. Following a call to this 
        // method, an element in the range given by index and count
        // which was previously located at index i will now be located at 
        // index index + (index + count - i - 1).
        //
        // This method uses the Array.Reverse method to reverse the
        // elements. 
        //
        public void Reverse(int index, int count) { 
            if (index < 0 || count < 0) { 
                ThrowHelper.ThrowArgumentOutOfRangeException( (index<0 ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
            } 

            if (_size - index < count)
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
            Array.Reverse(_items, index, count); 
            _version++;
        } 
 
        // Sorts the elements in this list.  Uses the default comparer and
        // Array.Sort. 
        public void Sort()
        {
            Sort(0, Count, null);
        } 

        // Sorts the elements in this list.  Uses Array.Sort with the 
        // provided comparer. 
        public 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 void Sort(int index, int count, IComparer comparer) {
            if (index < 0 || count < 0) { 
                ThrowHelper.ThrowArgumentOutOfRangeException( (index<0 ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
            } 
 
            if (_size - index < count)
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen); 

            Array.Sort(_items, index, count, comparer);
            _version++;
        } 

        public void Sort(Comparison comparison) { 
            if( comparison == null) { 
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
            } 

            if( _size > 0) {
                IComparer comparer = new Array.FunctorComparer(comparison);
                Array.Sort(_items, 0, _size, comparer); 
            }
        } 
 
        // ToArray returns a new Object array containing the contents of the List.
        // This requires copying the List, which is an O(n) operation. 
        public T[] ToArray() {
            T[] array = new T[_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.TrimExcess();
        // 
        public void TrimExcess() { 
            int threshold = (int)(((double)_items.Length) * 0.9);
            if( _size < threshold ) { 
                Capacity = _size;
            }
        }
 
        public bool TrueForAll(Predicate match) {
            if( match == null) { 
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match); 
            }
 
            for(int i = 0 ; i < _size; i++) {
                if( !match(_items[i])) {
                    return false;
                } 
            }
            return true; 
        } 

        [Serializable()] 
        public struct Enumerator : IEnumerator, System.Collections.IEnumerator
        {
            private List list;
            private int index; 
            private int version;
            private T current; 
 
            internal Enumerator(List list) {
                this.list = list; 
                index = 0;
                version = list._version;
                current = default(T);
            } 

            public void Dispose() { 
            } 

            public bool MoveNext() { 

                List localList = list;

                if (version == localList._version && ((uint)index < (uint)localList._size)) 
                {
                    current = localList._items[index]; 
                    index++; 
                    return true;
                } 
                return MoveNextRare();
            }

            private bool MoveNextRare() 
            {
                if (version != list._version) { 
                    ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumFailedVersion); 
                }
 
                index = list._size + 1;
                current = default(T);
                return false;
            } 

            public T Current { 
                get { 
                    return current;
                } 
            }

            Object System.Collections.IEnumerator.Current {
                get { 
                    if( index == 0 || index == list._size + 1) {
                         ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumOpCantHappen); 
                    } 
                    return Current;
                } 
            }

            void System.Collections.IEnumerator.Reset() {
                if (version != list._version) { 
                    ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumFailedVersion);
                } 
 
                index = 0;
                current = default(T); 
            }

        }
    } 
}
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
/*============================================================
** 
** Class:  List 
**
** Purpose: Implements a generic, dynamically sized list as an 
**          array.
**
**
===========================================================*/ 
namespace System.Collections.Generic {
 
    using System; 
    using System.Diagnostics;
    using System.Collections.ObjectModel; 
    using System.Security.Permissions;

    // Implements a variable-size List that uses an array of objects to store the
    // elements. A List has a capacity, which is the allocated length 
    // of the internal array. As elements are added to a List, the capacity
    // of the List is automatically increased as required by reallocating the 
    // internal array. 
    //
    [DebuggerTypeProxy(typeof(Mscorlib_CollectionDebugView<>))] 
    [DebuggerDisplay("Count = {Count}")]
    [Serializable()]

    public class List : IList, System.Collections.IList 
    {
        private const int _defaultCapacity = 4; 
 
        private T[] _items;
        private int _size; 
        private int _version;
        [NonSerialized]
        private Object _syncRoot;
 
        static T[]  _emptyArray = new T[0];
 
        // Constructs a List. The list is initially empty and has a capacity 
        // of zero. Upon adding the first element to the list the capacity is
        // increased to 16, and then increased in multiples of two as required. 
        public List() {
            _items = _emptyArray;
        }
 
        // Constructs a List 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 List(int capacity) { 
            if (capacity < 0) ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.capacity, ExceptionResource.ArgumentOutOfRange_SmallCapacity);
            _items = new T[capacity];
        }
 
        // Constructs a List, 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 List(IEnumerable collection) { 
            if (collection==null)
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection);

            ICollection c = collection as ICollection; 
            if( c != null) {
                int count = c.Count; 
                _items = new T[count]; 
                c.CopyTo(_items, 0);
                _size = count; 
            }
            else {
                _size = 0;
                _items = new T[_defaultCapacity]; 

                using(IEnumerator en = collection.GetEnumerator()) { 
                    while(en.MoveNext()) { 
                        Add(en.Current);
                    } 
                }
            }
        }
 
        // 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 int Capacity { 
            get { return _items.Length; }
            set {
                if (value != _items.Length) {
                    if (value < _size) { 
                        ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.value, ExceptionResource.ArgumentOutOfRange_SmallCapacity);
                    } 
 
                    if (value > 0) {
                        T[] newItems = new T[value]; 
                        if (_size > 0) {
                            Array.Copy(_items, 0, newItems, 0, _size);
                        }
                        _items = newItems; 
                    }
                    else { 
                        _items = _emptyArray; 
                    }
                } 
            }
        }

        // Read-only property describing how many elements are in the List. 
        public int Count {
            get { return _size; } 
        } 

        bool System.Collections.IList.IsFixedSize { 
            get { return false; }
        }

 
        // Is this List read-only?
        bool ICollection.IsReadOnly { 
            get { return false; } 
        }
 
        bool System.Collections.IList.IsReadOnly {
            get { return false; }
        }
 
        // Is this List synchronized (thread-safe)?
        bool System.Collections.ICollection.IsSynchronized { 
            get { return false; } 
        }
 
        // Synchronization root for this object.
        Object System.Collections.ICollection.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 T this[int index] {
            get { 
                // Fllowing trick can reduce the range check by one
                if ((uint) index >= (uint)_size) { 
                    ThrowHelper.ThrowArgumentOutOfRangeException(); 
                }
                return _items[index]; 
            }
            set {
                if ((uint) index >= (uint)_size) {
                    ThrowHelper.ThrowArgumentOutOfRangeException(); 
                }
                _items[index] = value; 
                _version++; 
            }
        } 

        private static bool IsCompatibleObject(object value) {
            if( (value is T) || ( value == null && !typeof(T).IsValueType) ) {
                return true; 
            }
            return false; 
        } 

        private static void VerifyValueType(object value) { 
            if( !IsCompatibleObject(value)) {
                ThrowHelper.ThrowWrongValueTypeArgumentException(value, typeof(T));
            }
        } 

        Object System.Collections.IList.this[int index] { 
            get { 
                return this[index];
            } 
            set {
                VerifyValueType(value);
                this[index] = (T) value;
            } 
        }
 
        // 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 void Add(T item) {
            if (_size == _items.Length) EnsureCapacity(_size + 1);
            _items[_size++] = item; 
            _version++;
        } 
 
        int System.Collections.IList.Add(Object item)
        { 
            VerifyValueType(item);
            Add((T) item);
            return Count - 1;
        } 

 
        // 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 void AddRange(IEnumerable collection) {
            InsertRange(_size, collection);
        } 

        public ReadOnlyCollection AsReadOnly() { 
            return new ReadOnlyCollection(this); 
        }
 
        // 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 int BinarySearch(int index, int count, T item, IComparer comparer) {
            if (index < 0 || count < 0) 
                ThrowHelper.ThrowArgumentOutOfRangeException( (index<0 ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
            if (_size - index < count) 
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen); 

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

        public int BinarySearch(T item)
        { 
            return BinarySearch(0,Count,item, null);
        } 
 
        public int BinarySearch(T item, IComparer comparer)
        { 
            return BinarySearch(0,Count,item,comparer);
        }

 
        // Clears the contents of List.
        public void Clear() { 
            if (_size > 0) 
            {
                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++;
        } 

        // Contains returns true if the specified element is in the List. 
        // It does a linear, O(n) search.  Equality is determined by calling 
        // item.Equals().
        // 
        public bool Contains(T item) {
            if ((Object) item == null) {
                for(int i=0; i<_size; i++)
                    if ((Object) _items[i] == null) 
                        return true;
                return false; 
            } 
            else {
                EqualityComparer c = EqualityComparer.Default; 
                for(int i=0; i<_size; i++) {
                    if (c.Equals(_items[i], item)) return true;
                }
                return false; 
            }
        } 
 
        bool System.Collections.IList.Contains(Object item)
        { 
            if(IsCompatibleObject(item)) {
                return Contains((T) item);
            }
            return false; 
        }
 
        public List ConvertAll(Converter converter) { 
            if( converter == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.converter); 
            }

            List list = new List(_size);
            for( int i = 0; i< _size; i++) { 
                list._items[i] = converter(_items[i]);
            } 
            list._size = _size; 
            return list;
        } 

        // Copies this List into array, which must be of a
        // compatible array type.
        // 
        public void CopyTo(T[] array) {
            CopyTo(array, 0); 
        } 

        // Copies this List into array, which must be of a 
        // compatible array type.
        //
        void System.Collections.ICollection.CopyTo(Array array, int arrayIndex) {
            if ((array != null) && (array.Rank != 1)) { 
                ThrowHelper.ThrowArgumentException(ExceptionResource.Arg_RankMultiDimNotSupported);
            } 
 
            try {
                // Array.Copy will check for NULL. 
                Array.Copy(_items, 0, array, arrayIndex, _size);
            }
            catch(ArrayTypeMismatchException){
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidArrayType); 
            }
        } 
 
        // 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 void CopyTo(int index, T[] array, int arrayIndex, int count) {
            if (_size - index < count) { 
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
            } 
 
            // Delegate rest of error checking to Array.Copy.
            Array.Copy(_items, index, array, arrayIndex, count); 
        }

        public void CopyTo(T[] array, int arrayIndex) {
            // Delegate rest of error checking to Array.Copy. 
            Array.Copy(_items, 0, array, arrayIndex, _size);
        } 
 
        // 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; 
            }
        } 

        public bool Exists(Predicate match) {
            return FindIndex(match) != -1;
        } 

        public T Find(Predicate match) { 
            if( match == null) { 
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
            } 

            for(int i = 0 ; i < _size; i++) {
                if(match(_items[i])) {
                    return _items[i]; 
                }
            } 
            return default(T); 
        }
 
        public List FindAll(Predicate match) {
            if( match == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
            } 

            List list = new List(); 
            for(int i = 0 ; i < _size; i++) { 
                if(match(_items[i])) {
                    list.Add(_items[i]); 
                }
            }
            return list;
        } 

        public int FindIndex(Predicate match) { 
            return FindIndex(0, _size, match); 
        }
 
        public int FindIndex(int startIndex, Predicate match) {
           return FindIndex( startIndex, _size - startIndex, match);
        }
 
        public int FindIndex(int startIndex, int count, Predicate match) {
            if( (uint)startIndex > (uint)_size ) { 
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index); 
            }
 
            if (count < 0 || startIndex > _size - count) {
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_Count);
            }
 
            if( match == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match); 
            } 

            int endIndex = startIndex + count; 
            for( int i = startIndex; i < endIndex; i++) {
                if( match(_items[i])) return i;
            }
            return -1; 
        }
 
        public T FindLast(Predicate match) { 
            if( match == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match); 
            }

            for(int i = _size - 1 ; i >= 0; i--) {
                if(match(_items[i])) { 
                    return _items[i];
                } 
            } 
            return default(T);
        } 

        public int FindLastIndex(Predicate match) {
            return FindLastIndex( _size - 1, _size, match);
        } 

        public int FindLastIndex(int startIndex, Predicate match) { 
           return FindLastIndex( startIndex, startIndex + 1, match); 
        }
 
        public int FindLastIndex(int startIndex, int count, Predicate match) {
            if( match == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
            } 

            if(_size == 0) { 
                // Special case for 0 length List 
                if( startIndex != -1) {
                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index); 
                }
            }
            else {
                // Make sure we're not out of range 
                if ( (uint)startIndex >= (uint)_size) {
                    ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.startIndex, ExceptionResource.ArgumentOutOfRange_Index); 
                } 
            }
 
            // 2nd have of this also catches when startIndex == MAXINT, so MAXINT - 0 + 1 == -1, which is < 0.
            if (count < 0 || startIndex - count + 1 < 0) {
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_Count);
            } 

            int endIndex = startIndex - count; 
            for( int i = startIndex; i > endIndex; i--) { 
                if( match(_items[i])) {
                    return i; 
                }
            }
            return -1;
        } 

 
        public void ForEach(Action action) { 
            if( action == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match); 
            }

            for(int i = 0 ; i < _size; i++) {
                action(_items[i]); 
            }
        } 
 
        // 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 Enumerator GetEnumerator() { 
            return new Enumerator(this);
        } 
 
        /// 
        IEnumerator IEnumerable.GetEnumerator() { 
            return new Enumerator(this);
        }

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { 
            return new Enumerator(this);
        } 
 
        public List GetRange(int index, int count) {
            if (index < 0 || count < 0) { 
                ThrowHelper.ThrowArgumentOutOfRangeException( (index<0 ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
            }

            if (_size - index < count) { 
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
            } 
 
            List list = new List(count);
            Array.Copy(_items, index, list._items, 0, count); 
            list._size = count;
            return list;
        }
 

        // 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 int IndexOf(T item) {
            return Array.IndexOf(_items, item, 0, _size); 
        } 

        int System.Collections.IList.IndexOf(Object item) 
        {
            if(IsCompatibleObject(item)) {
                return IndexOf((T)item);
            } 
            return -1;
        } 
 
        // 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 
        // index 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 int IndexOf(T item, int index) {
            if (index > _size) 
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_Index);
            return Array.IndexOf(_items, item, index, _size - index);
        }
 
        // 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 
        // index 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 int IndexOf(T item, int index, int count) {
            if (index > _size) 
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_Index); 

            if (count <0 || index > _size - count) ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count, ExceptionResource.ArgumentOutOfRange_Count); 

            return Array.IndexOf(_items, item, index, 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 void Insert(int index, T item) { 
            // Note that insertions at the end are legal.
            if ((uint) index > (uint)_size) {
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_ListInsert);
            } 
            if (_size == _items.Length) EnsureCapacity(_size + 1);
            if (index < _size) { 
                Array.Copy(_items, index, _items, index + 1, _size - index); 
            }
            _items[index] = item; 
            _size++;
            _version++;
        }
 
        void System.Collections.IList.Insert(int index, Object item)
        { 
            VerifyValueType(item); 
            Insert(index, (T) item);
        } 

        // 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 List's size.
        // 
        public void InsertRange(int index, IEnumerable collection) { 
            if (collection==null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.collection); 
            }

            if ((uint)index > (uint)_size) {
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_Index); 
            }
 
            ICollection c = collection as ICollection; 
            if( c != null ) {    // if collection is ICollection
                int count = c.Count; 
                if (count > 0) {
                    EnsureCapacity(_size + count);
                    if (index < _size) {
                        Array.Copy(_items, index, _items, index + count, _size - index); 
                    }
 
                    // If we're inserting a List into itself, we want to be able to deal with that. 
                    if (this == c) {
                        // Copy first part of _items to insert location 
                        Array.Copy(_items, 0, _items, index, index);
                        // Copy last part of _items back to inserted location
                        Array.Copy(_items, index+count, _items, index*2, _size-index);
                    } 
                    else {
                        T[] itemsToInsert = new T[count]; 
                        c.CopyTo(itemsToInsert, 0); 
                        itemsToInsert.CopyTo(_items, index);
                    } 
                    _size += count;
                }
            }
            else { 
                using(IEnumerator en = collection.GetEnumerator()) {
                    while(en.MoveNext()) { 
                        Insert(index++, en.Current); 
                    }
                } 
            }
            _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 int LastIndexOf(T item) 
        {
            return LastIndexOf(item, _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
        // index 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 int LastIndexOf(T item, int index) 
        {
            if (index >= _size)
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.index, ExceptionResource.ArgumentOutOfRange_Index);
            return LastIndexOf(item, index, index + 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
        // index 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 int LastIndexOf(T item, int index, int count) { 
            if (_size == 0) {
                return -1; 
            }

            if (index < 0 || count < 0) {
                ThrowHelper.ThrowArgumentOutOfRangeException( (index<0 ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_NeedNonNegNum); 
            }
 
            if (index >= _size || count > index + 1) { 
                ThrowHelper.ThrowArgumentOutOfRangeException((index >= _size ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_BiggerThanCollection);
            } 

            return Array.LastIndexOf(_items, item, index, count);
        }
 
        // Removes the element at the given index. The size of the list is
        // decreased by one. 
        // 
        public bool Remove(T item) {
            int index = IndexOf(item); 
            if (index >= 0) {
                RemoveAt(index);
                return true;
            } 

            return false; 
        } 

        void System.Collections.IList.Remove(Object item) 
        {
            if(IsCompatibleObject(item)) {
                Remove((T) item);
            } 
        }
 
        // This method removes all items which matches the predicate. 
        // The complexity is O(n).
        public int RemoveAll(Predicate match) { 
            if( match == null) {
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
            }
 
            int freeIndex = 0;   // the first free slot in items array
 
            // Find the first item which needs to be removed. 
            while( freeIndex < _size && !match(_items[freeIndex])) freeIndex++;
            if( freeIndex >= _size) return 0; 

            int current = freeIndex + 1;
            while( current < _size) {
                // Find the first item which needs to be kept. 
                while( current < _size && match(_items[current])) current++;
 
                if( current < _size) { 
                    // copy item to the free slot.
                    _items[freeIndex++] = _items[current++]; 
                }
            }

            Array.Clear(_items, freeIndex, _size - freeIndex); 
            int result = _size - freeIndex;
            _size = freeIndex; 
            _version++; 
            return result;
        } 

        // Removes the element at the given index. The size of the list is
        // decreased by one.
        // 
        public void RemoveAt(int index) {
            if ((uint)index >= (uint)_size) { 
                ThrowHelper.ThrowArgumentOutOfRangeException(); 
            }
            _size--; 
            if (index < _size) {
                Array.Copy(_items, index + 1, _items, index, _size - index);
            }
            _items[_size] = default(T); 
            _version++;
        } 
 
        // Removes a range of elements from this list.
        // 
        public void RemoveRange(int index, int count) {
            if (index < 0 || count < 0) {
                ThrowHelper.ThrowArgumentOutOfRangeException( (index<0 ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
            } 

            if (_size - index < count) 
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen); 

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

        // Reverses the elements in this list.
        public void Reverse() {
            Reverse(0, Count); 
        }
 
        // Reverses the elements in a range of this list. Following a call to this 
        // method, an element in the range given by index and count
        // which was previously located at index i will now be located at 
        // index index + (index + count - i - 1).
        //
        // This method uses the Array.Reverse method to reverse the
        // elements. 
        //
        public void Reverse(int index, int count) { 
            if (index < 0 || count < 0) { 
                ThrowHelper.ThrowArgumentOutOfRangeException( (index<0 ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
            } 

            if (_size - index < count)
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen);
            Array.Reverse(_items, index, count); 
            _version++;
        } 
 
        // Sorts the elements in this list.  Uses the default comparer and
        // Array.Sort. 
        public void Sort()
        {
            Sort(0, Count, null);
        } 

        // Sorts the elements in this list.  Uses Array.Sort with the 
        // provided comparer. 
        public 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 void Sort(int index, int count, IComparer comparer) {
            if (index < 0 || count < 0) { 
                ThrowHelper.ThrowArgumentOutOfRangeException( (index<0 ? ExceptionArgument.index : ExceptionArgument.count), ExceptionResource.ArgumentOutOfRange_NeedNonNegNum);
            } 
 
            if (_size - index < count)
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_InvalidOffLen); 

            Array.Sort(_items, index, count, comparer);
            _version++;
        } 

        public void Sort(Comparison comparison) { 
            if( comparison == null) { 
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match);
            } 

            if( _size > 0) {
                IComparer comparer = new Array.FunctorComparer(comparison);
                Array.Sort(_items, 0, _size, comparer); 
            }
        } 
 
        // ToArray returns a new Object array containing the contents of the List.
        // This requires copying the List, which is an O(n) operation. 
        public T[] ToArray() {
            T[] array = new T[_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.TrimExcess();
        // 
        public void TrimExcess() { 
            int threshold = (int)(((double)_items.Length) * 0.9);
            if( _size < threshold ) { 
                Capacity = _size;
            }
        }
 
        public bool TrueForAll(Predicate match) {
            if( match == null) { 
                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.match); 
            }
 
            for(int i = 0 ; i < _size; i++) {
                if( !match(_items[i])) {
                    return false;
                } 
            }
            return true; 
        } 

        [Serializable()] 
        public struct Enumerator : IEnumerator, System.Collections.IEnumerator
        {
            private List list;
            private int index; 
            private int version;
            private T current; 
 
            internal Enumerator(List list) {
                this.list = list; 
                index = 0;
                version = list._version;
                current = default(T);
            } 

            public void Dispose() { 
            } 

            public bool MoveNext() { 

                List localList = list;

                if (version == localList._version && ((uint)index < (uint)localList._size)) 
                {
                    current = localList._items[index]; 
                    index++; 
                    return true;
                } 
                return MoveNextRare();
            }

            private bool MoveNextRare() 
            {
                if (version != list._version) { 
                    ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumFailedVersion); 
                }
 
                index = list._size + 1;
                current = default(T);
                return false;
            } 

            public T Current { 
                get { 
                    return current;
                } 
            }

            Object System.Collections.IEnumerator.Current {
                get { 
                    if( index == 0 || index == list._size + 1) {
                         ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumOpCantHappen); 
                    } 
                    return Current;
                } 
            }

            void System.Collections.IEnumerator.Reset() {
                if (version != list._version) { 
                    ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumFailedVersion);
                } 
 
                index = 0;
                current = default(T); 
            }

        }
    } 
}
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
                        

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