ModelTreeEnumerator.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Framework / MS / Internal / Controls / ModelTreeEnumerator.cs / 1 / ModelTreeEnumerator.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
//--------------------------------------------------------------------------- 
using System; 
using System.Collections;
using System.ComponentModel; 
using System.Diagnostics;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data; 
using MS.Internal.Controls;
using MS.Internal.Data; 
using MS.Utility; 

namespace MS.Internal.Controls 
{
    internal abstract class ModelTreeEnumerator : IEnumerator
    {
        internal ModelTreeEnumerator(object content) 
        {
            _content = content; 
        } 

        #region IEnumerator 

        object IEnumerator.Current
        {
            get 
            {
                return this.Current; 
            } 
        }
 
        bool IEnumerator.MoveNext()
        {
            return this.MoveNext();
        } 

        void IEnumerator.Reset() 
        { 
            this.Reset();
        } 

        #endregion

        #region Protected 

        protected object Content 
        { 
            get
            { 
                return _content;
            }
        }
 
        protected int Index
        { 
            get 
            {
                return _index; 
            }

            set
            { 
                _index = value;
            } 
        } 

        protected virtual object Current 
        {
            get
            {
                // Don't VerifyUnchanged(); According to MSDN: 
                //     If the collection is modified between MoveNext and Current,
                //     Current will return the element that it is set to, even if 
                //     the enumerator is already invalidated. 

                if (_index == 0) 
                {
                    return _content;
                }
 
#pragma warning disable 1634 // about to use PreSharp message numbers - unknown to C#
                // Fall through -- can't enumerate (before beginning or after end) 
#pragma warning suppress 6503 
                throw new InvalidOperationException(SR.Get(SRID.EnumeratorInvalidOperation));
                // above exception is part of the IEnumerator.Current contract when moving beyond begin/end 
#pragma warning restore 1634
            }
        }
 
        protected virtual bool MoveNext()
        { 
            if (_index < 1) 
            {
                // Singular content, can move next to 0 and that's it. 
                _index++;

                if (_index == 0)
                { 
                    // don't call VerifyUnchanged if we're returning false anyway.
                    // This permits users to change the Content after enumerating 
                    // the content (e.g. in the invalidation callback of an inherited 
                    // property).  See bug 955389.
 
                    VerifyUnchanged();
                    return true;
                }
            } 

            return false; 
        } 

        protected virtual void Reset() 
        {
            VerifyUnchanged();
            _index = -1;
        } 

        protected abstract bool IsUnchanged 
        { 
            get;
        } 

        protected void VerifyUnchanged()
        {
            // If the content has changed, then throw an exception 
            if (!IsUnchanged)
            { 
                throw new InvalidOperationException(SR.Get(SRID.EnumeratorVersionChanged)); 
            }
        } 

        #endregion

        #region Data 

        private int _index = -1; 
        private object _content; 

        #endregion 
    }

    internal class ContentModelTreeEnumerator : ModelTreeEnumerator
    { 
        internal ContentModelTreeEnumerator(ContentControl contentControl, object content) : base(content)
        { 
            Debug.Assert(contentControl != null, "contentControl should be non-null."); 

            _owner = contentControl; 
        }

        protected override bool IsUnchanged
        { 
            get
            { 
                return Object.ReferenceEquals(Content, _owner.Content); 
            }
        } 

        private ContentControl _owner;
    }
 
    internal class HeaderedContentModelTreeEnumerator : ModelTreeEnumerator
    { 
        internal HeaderedContentModelTreeEnumerator(HeaderedContentControl headeredContentControl, object content, object header) : base(header) 
        {
            Debug.Assert(headeredContentControl != null, "headeredContentControl should be non-null."); 
            Debug.Assert(header != null, "Header should be non-null. If Header was null, the base ContentControl enumerator should have been used.");

            _owner = headeredContentControl;
            _content = content; 
        }
 
        protected override object Current 
        {
            get 
            {
                if ((Index == 1) && (_content != null))
                {
                    return _content; 
                }
 
                return base.Current; 
            }
        } 

        protected override bool MoveNext()
        {
            if (_content != null) 
            {
                if (Index == 0) 
                { 
                    // Moving from the header to content
                    Index++; 
                    VerifyUnchanged();
                    return true;
                }
                else if (Index == 1) 
                {
                    // Going from content to the end 
                    Index++; 
                    return false;
                } 
            }

            return base.MoveNext();
        } 

        protected override bool IsUnchanged 
        { 
            get
            { 
                object header = Content;    // Header was passed to the base so that it would appear in index 0
                return Object.ReferenceEquals(header, _owner.Header) &&
                       Object.ReferenceEquals(_content, _owner.Content);
            } 
        }
 
        private HeaderedContentControl _owner; 
        private object _content;
    } 

    internal class HeaderedItemsModelTreeEnumerator : ModelTreeEnumerator
    {
        internal HeaderedItemsModelTreeEnumerator(HeaderedItemsControl headeredItemsControl, IEnumerator items, object header) : base(header) 
        {
            Debug.Assert(headeredItemsControl != null, "headeredItemsControl should be non-null."); 
            Debug.Assert(items != null, "items should be non-null."); 
            Debug.Assert(header != null, "header should be non-null. If Header was null, the base ItemsControl enumerator should have been used.");
 
            _owner = headeredItemsControl;
            _items = items;
        }
 
        protected override object Current
        { 
            get 
            {
                if (Index > 0) 
                {
                    return _items.Current;
                }
 
                return base.Current;
            } 
        } 

        protected override bool MoveNext() 
        {
            if (Index >= 0)
            {
                Index++; 
                return _items.MoveNext();
            } 
 
            return base.MoveNext();
        } 

        protected override void Reset()
        {
            base.Reset(); 
            _items.Reset();
        } 
 
        protected override bool IsUnchanged
        { 
            get
            {
                object header = Content;    // Header was passed to the base so that it would appear in index 0
                return Object.ReferenceEquals(header, _owner.Header); 
            }
        } 
 
        private HeaderedItemsControl _owner;
        private IEnumerator _items; 
    }
}

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

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