TextElementEnumerator.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Framework / System / Windows / Documents / TextElementEnumerator.cs / 1 / TextElementEnumerator.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// 
// Description: IEnumerator for TextRange and TextElement content. 
//
// 
// History:
//  05/27/2003 : [....] - Created
//
//--------------------------------------------------------------------------- 

using System; 
using System.Collections; 
using System.Collections.Generic;
using MS.Internal; 
using System.Text;
using MS.Utility;
using System.Windows.Controls;
 
#pragma warning disable 1634, 1691  // suppressing PreSharp warnings
 
namespace System.Windows.Documents 
{
    internal class TextElementEnumerator : IEnumerator where TextElementType : TextElement 
    {
        //-----------------------------------------------------
        //
        //  Constructors 
        //
        //----------------------------------------------------- 
 
        #region Constructors
 
        // Creates an enumerator instance.
        // Null start/end creates an empty enumerator.
        internal TextElementEnumerator(TextPointer start, TextPointer end)
        { 
            Invariant.Assert(start != null && end != null || start == null && end == null, "If start is null end should be null!");
 
            _start = start; 
            _end = end;
 
            // Remember what generation the backing store was in when we started,
            // so we can throw if this enumerator is accessed after content has
            // changed.
            if (_start != null) 
            {
                _generation = _start.TextContainer.Generation; 
            } 
        }
 
        #endregion Constructors

        //------------------------------------------------------
        // 
        //  Public Methods
        // 
        //----------------------------------------------------- 

        #region Public Methods 

        public void Dispose()
        {
            // Empty the enumerator 
            _current = null;
            _navigator = null; 
        } 

        object System.Collections.IEnumerator.Current 
        {
            get
            {
                return this.Current; 
            }
        } 
 
        /// 
        /// Return the current object this enumerator is pointing to.  This is 
        /// generally a FrameworkElement, TextElement, an embedded
        /// object, or Text content.
        /// 
        ///  
        /// According to the IEnumerator spec, the Current property keeps
        /// the element even after the content has been modified 
        /// (even if the current element has been deleted from the collection). 
        /// This is unlike to Reset or MoveNext which throw after any content change.
        ///  
        public TextElementType Current
        {
            get
            { 
                if (_navigator == null)
                { 
                    #pragma warning suppress 6503 // IEnumerator.Current is documented to throw this exception 
                    throw new InvalidOperationException(SR.Get(SRID.EnumeratorNotStarted));
                } 

                if (_current == null)
                {
                    #pragma warning suppress 6503 // IEnumerator.Current is documented to throw this exception 
                    throw new InvalidOperationException(SR.Get(SRID.EnumeratorReachedEnd));
                } 
 
                return _current;
            } 
        }

        /// 
        /// Advance the enumerator to the next object in the range.  Return true if content 
        /// was found.
        ///  
        public bool MoveNext() 
        {
            // Throw if the tree has been modified since this enumerator was created. 
            if (_start != null && _generation != _start.TextContainer.Generation)
            {
                throw new InvalidOperationException(SR.Get(SRID.EnumeratorVersionChanged));
            } 

            // Return false if the collection is empty 
            if (_start == null || _start.CompareTo(_end) == 0) 
            {
                return false; 
            }

            // Return false if the navigator reached the end of the collection
            if (_navigator != null && _navigator.CompareTo(_end) >= 0) 
            {
                return false; 
            } 

            // Advance the navigator 
            if (_navigator == null)
            {
                // Set it to the first element for the very first move
                _navigator = new TextPointer(_start); 
                _navigator.MoveToNextContextPosition(LogicalDirection.Forward);
            } 
            else 
            {
                // Move to the next element in the collection 
                Invariant.Assert(_navigator.GetPointerContext(LogicalDirection.Backward) == TextPointerContext.ElementStart,
                    "Unexpected run type in TextElementEnumerator");

                _navigator.MoveToElementEdge(ElementEdge.AfterEnd); 
                _navigator.MoveToNextContextPosition(LogicalDirection.Forward);
            } 
 
            // Update current cache
            if (_navigator.CompareTo(_end) < 0) 
            {
                _current = (TextElementType)_navigator.Parent;
            }
            else 
            {
                _current = null; 
            } 

            // Return true if the content was found 
            return (_current != null);
        }

        ///  
        /// Reset the enumerator to the start of the range.
        ///  
        public void Reset() 
        {
            // Throw if the tree has been modified since this enumerator was created. 
            if (_start != null && _generation != _start.TextContainer.Generation)
            {
                throw new InvalidOperationException(SR.Get(SRID.EnumeratorVersionChanged));
            } 

            _navigator = null; 
            _current = null; 
        }
 
        #endregion Public Methods

        //------------------------------------------------------
        // 
        //  Public Properties
        // 
        //------------------------------------------------------ 

        #region Public Properties 

        #endregion Public Properties

        //----------------------------------------------------- 
        //
        //  Public Events 
        // 
        //------------------------------------------------------
 
        #region Public Events

        #endregion Public Events
 
        //-----------------------------------------------------
        // 
        //  Protected Methods 
        //
        //----------------------------------------------------- 

        #region Protected Methods

        #endregion Protected Events 

        //----------------------------------------------------- 
        // 
        //  Internal Methods
        // 
        //------------------------------------------------------

        #region Internal Methods
 
        #endregion Internal methods
 
        //----------------------------------------------------- 
        //
        //  Internal Properties 
        //
        //------------------------------------------------------

        #region Internal Properties 

        #endregion Internal Properties 
 
        //------------------------------------------------------
        // 
        //  Internal Events
        //
        //-----------------------------------------------------
 
        #region Internal Events
 
        #endregion Internal Events 

        //------------------------------------------------------ 
        //
        //  Private Properties
        //
        //----------------------------------------------------- 

        #region Private Properties 
 
        #endregion Private Properties
 
        //-----------------------------------------------------
        //
        //  Private Fields
        // 
        //-----------------------------------------------------
 
        #region Private Fields 

        // Edges of the span to enumerator over. 
        private readonly TextPointer _start;
        private readonly TextPointer _end;

        // Backing store generation when this enumerator was created. 
        private readonly uint _generation;
 
        // Current position in the enumeration. 
        private TextPointer _navigator;
 
        // Calculated content at the current position.
        private TextElementType _current;

        #endregion Private Fields 
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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