JournalEntryStack.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Framework / MS / Internal / Navigation / JournalEntryStack.cs / 1305600 / JournalEntryStack.cs
                        
                        
                            using System; 
using System.Collections;
using System.Collections.Specialized;
using System.Collections.Generic;
using System.Diagnostics; 
using System.Windows.Threading;
 
using MS.Internal; 
using MS.Internal.AppModel;
using MS.Utility; 
using System.ComponentModel;

namespace System.Windows.Navigation
{ 

    ///  
    /// This is the base class for the JournalEntryBackStack and JournalEntryForwardStack 
    /// classes.
    ///  
    internal abstract class JournalEntryStack : IEnumerable, INotifyCollectionChanged
    {
        internal JournalEntryStack(Journal journal)
        { 
            _journal = journal;
        } 
 
        internal void OnCollectionChanged()
        { 
            if (CollectionChanged != null)
            {
                CollectionChanged(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
            } 
        }
 
        internal JournalEntryFilter Filter 
        {
            get { return _filter; } 
            set { _filter = value; }
        }

        internal IEnumerable GetLimitedJournalEntryStackEnumerable() 
        {
            if (_ljese == null) 
            { 
                _ljese = new LimitedJournalEntryStackEnumerable(this);
            } 
            return _ljese;
        }

        LimitedJournalEntryStackEnumerable _ljese; 
        protected JournalEntryFilter _filter;
        public event NotifyCollectionChangedEventHandler CollectionChanged; 
        public abstract IEnumerator GetEnumerator(); 
        protected Journal _journal;
    } 

    /// 
    /// This class exists to provide an IEnumerator over the BackStack.
    ///  
    internal class JournalEntryBackStack : JournalEntryStack
    { 
        public JournalEntryBackStack(Journal journal) 
            : base(journal)
        { 
        }

        public override IEnumerator GetEnumerator()
        { 
            //Debug.WriteLine("Getting BackStack");
            return new JournalEntryStackEnumerator(_journal, _journal.CurrentIndex - 1, -1, this.Filter); 
        } 
    }
 
    /// 
    /// This class exists to provide an IEnumerator over the ForwardStack.
    /// 
    internal class JournalEntryForwardStack : JournalEntryStack 
    {
        public JournalEntryForwardStack(Journal journal) 
            : base(journal) 
        {
        } 

        public override IEnumerator GetEnumerator()
        {
            //Debug.WriteLine("Getting ForwardStack"); 
            return new JournalEntryStackEnumerator(_journal, _journal.CurrentIndex + 1, 1, this.Filter);
        } 
    } 

    ///  
    /// This will enumerate over the navigable JournalEntries in the journal, starting at start,
    /// going in the direction of delta, and returning no more than _viewLimit values.
    /// This is used for display purposes.
    ///  
    internal class JournalEntryStackEnumerator : IEnumerator
    { 
        public JournalEntryStackEnumerator(Journal journal, int start, int delta, JournalEntryFilter filter) 
        {
            _journal = journal; 
            _version = journal.Version;
            _start = start;
            _delta = delta;
            _filter = filter; 
            this.Reset();
        } 
 
        public void Reset()
        { 
            _next = _start;
            _current = null;
        }
 
        public bool MoveNext()
        { 
            VerifyUnchanged(); 

            while ((_next >= 0) && (_next < _journal.TotalCount)) 
            {
                _current = _journal[_next];
                _next += _delta;
                if ((_filter == null) || _filter(_current)) 
                {
                    Debug.Assert(_current != null, "If we are returning true, our current cannot be null"); 
                    return true; 
                }
            } 

            _current = null;
            return false;
        } 

        public object Current 
        { 
            get { return _current; }
        } 

        /// 
        /// Verifies that the journal has not been changed since this enumerator was created
        ///  
        protected void VerifyUnchanged()
        { 
            if (_version != _journal.Version) 
            {
                throw new InvalidOperationException(SR.Get(SRID.EnumeratorVersionChanged)); 
            }
        }

        Journal _journal; 
        int _start;
        int _delta; 
        int _next; 
        JournalEntry _current;
        JournalEntryFilter _filter; 
        int _version;
    }

    internal class LimitedJournalEntryStackEnumerable : IEnumerable, INotifyCollectionChanged 
    {
        internal LimitedJournalEntryStackEnumerable(IEnumerable ieble) 
        { 
            _ieble = ieble;
            INotifyCollectionChanged ichildnotify = ieble as INotifyCollectionChanged; 
            if (ichildnotify != null)
            {
                ichildnotify.CollectionChanged += new NotifyCollectionChangedEventHandler(PropogateCollectionChanged);
            } 
        }
 
        public IEnumerator GetEnumerator() 
        {
            return new LimitedJournalEntryStackEnumerator(_ieble, DefaultMaxMenuEntries); 
        }

        internal void PropogateCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        { 
            if (CollectionChanged != null)
            { 
                CollectionChanged(this, e); 
            }
        } 

        private const uint  DefaultMaxMenuEntries = 9; // the maximum number of items in the dropdown menus

        public event NotifyCollectionChangedEventHandler CollectionChanged; 

        private IEnumerable _ieble; 
    } 

    internal class LimitedJournalEntryStackEnumerator : IEnumerator 
    {
        internal LimitedJournalEntryStackEnumerator(IEnumerable ieble, uint viewLimit)
        {
            _ienum = ieble.GetEnumerator(); 
            _viewLimit = viewLimit;
        } 
 
        public void Reset()
        { 
            _itemsReturned = 0;
            _ienum.Reset();
        }
 
        public bool MoveNext()
        { 
            bool success; 
            if (_itemsReturned == _viewLimit)
            { 
                success = false;
            }
            else
            { 
                success = _ienum.MoveNext();
                if (success) 
                { 
                    _itemsReturned++;
                } 
            }
            return success;
        }
 
        public object Current
        { 
            get { return _ienum.Current; } 
        }
 
        private uint _itemsReturned;
        private uint _viewLimit;
        private IEnumerator _ienum;
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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JournalEntryStack.cs source code in C# .NET

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