LogicalTreeHelper.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Framework / System / Windows / LogicalTreeHelper.cs / 1 / LogicalTreeHelper.cs
                        

                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: The LogicalTreeHelper class contains static methods that are 
//  useful for performing common tasks with logical tree nodes.  There's nothing 
//  here that the end user can't do themselves - but we do it for them and
//  gather them up here. 
//
// History:
//  07/28/2003 : [....] - Initial creation
// 
//---------------------------------------------------------------------------
 
using System; 
using System.Collections;   // In order to use IEnumerator
using System.Diagnostics; 
using MS.Utility;           // In order to use SR.Get and SRID

namespace System.Windows
{ 
/*
    public delegate bool ParentTraversalCallback(FrameworkElement parentFE, FrameworkContentElement parentFCE, object data); 
    public delegate bool ChildTraversalCallback(FrameworkElement childFE, FrameworkContentElement childFCE, object child, object data); 
*/
 
/// 
/// Static helper functions for dealing with the logical tree
/// 
public static class LogicalTreeHelper 
{
    //----------------------------------------------------- 
    // 
    //  Constructors
    // 
    //-----------------------------------------------------

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

    // None 

    //------------------------------------------------------
    //
    //  Public Methods 
    //
    //------------------------------------------------------ 
 
    #region Public Methods
 
    /// 
    /// Given an element in the logical tree to start searching from,
    /// searches all its descendent nodes in the logical tree a node whose Name
    /// matches the specified elementName. 
    /// The given DependencyObject must be either a FrameworkElement or FrameworkContentElement.
    ///  
    ///  
    /// We're searching in a depth-first manner.  Review this if this turns out
    ///  to be a performance problem.  We're doing this first because it's easy 
    ///  and light on memory usage as compared to breadth-first.
    /// ([....]):It would be cool if the DFID (depth-first iterative-deepening)
    ///  algorithm would be useful here.
    ///  
    public static DependencyObject FindLogicalNode( DependencyObject logicalTreeNode, string elementName )
    { 
        if( logicalTreeNode == null ) 
        {
            throw new ArgumentNullException("logicalTreeNode"); 
        }
        if( elementName == null )
        {
            throw new ArgumentNullException("elementName"); 
        }
        if( elementName == String.Empty ) 
        { 
            throw new ArgumentException(SR.Get(SRID.StringEmpty), "elementName");
        } 

        DependencyObject namedElement = null;
        DependencyObject childNode = null;
 
        // Check given node against named element.
        IFrameworkInputElement selfNode = logicalTreeNode as IFrameworkInputElement; 
        if( selfNode != null ) 
        {
            if( selfNode.Name == elementName ) 
            {
                namedElement = logicalTreeNode;
            }
        } 

        if( namedElement == null ) 
        { 
            // Nope, the given node isn't it.  See if we can check children.
            IEnumerator childEnumerator = null; 

            childEnumerator = LogicalTreeHelper.GetLogicalChildren(logicalTreeNode);

            // If we can enumerate, check the children. 
            if( childEnumerator != null )
            { 
                childEnumerator.Reset(); 
                while( namedElement == null &&
                       childEnumerator.MoveNext() == true) 
                {
                    childNode = childEnumerator.Current as DependencyObject;

                    if( childNode != null ) 
                    {
                        namedElement = FindLogicalNode( childNode, elementName ); 
                    } 
                }
            } 
        }

        // Return what we can find - may be null.
        return namedElement; 
    }
 
    ///  
    /// Get the logical parent of the given DependencyObject.
    /// The given DependencyObject must be either a FrameworkElement or FrameworkContentElement 
    /// to have a logical parent.
    /// 
    public static DependencyObject GetParent(DependencyObject current)
    { 
        if (current == null)
        { 
            throw new ArgumentNullException("current"); 
        }
 
        FrameworkElement fe = current as FrameworkElement;
        if (fe != null)
        {
            return fe.Parent; 
        }
 
        FrameworkContentElement fce = current as FrameworkContentElement; 
        if (fce != null)
        { 
            return fce.Parent;
        }

        return null; 
    }
 
    ///  
    /// Get the logical children for the given DependencyObject.
    /// The given DependencyObject must be either a FrameworkElement or FrameworkContentElement 
    /// to have logical children.
    /// 
    public static IEnumerable GetChildren(DependencyObject current)
    { 
        if (current == null)
        { 
            throw new ArgumentNullException("current"); 
        }
 
        FrameworkElement fe = current as FrameworkElement;
        if (fe != null)
        {
            return new EnumeratorWrapper(fe.LogicalChildren); 
        }
 
        FrameworkContentElement fce = current as FrameworkContentElement; 
        if (fce != null)
        { 
            return new EnumeratorWrapper(fce.LogicalChildren);
        }

        return EnumeratorWrapper.Empty; 
    }
 
    ///  
    /// Get the logical children for the given FrameworkElement
    ///  
    public static IEnumerable GetChildren(FrameworkElement current)
    {
        if (current == null)
        { 
            throw new ArgumentNullException("current");
        } 
 
        return new EnumeratorWrapper(current.LogicalChildren);
    } 

    /// 
    /// Get the logical children for the given FrameworkContentElement
    ///  
    public static IEnumerable GetChildren(FrameworkContentElement current)
    { 
        if (current == null) 
        {
            throw new ArgumentNullException("current"); 
        }

        return new EnumeratorWrapper(current.LogicalChildren);
    } 

    ///  
    /// Attempts to bring this element into view by originating a RequestBringIntoView event. 
    /// 
    public static void BringIntoView(DependencyObject current) 
    {
        if (current == null)
        {
            throw new ArgumentNullException("current"); 
        }
 
        FrameworkElement fe = current as FrameworkElement; 
        if (fe != null)
        { 
            fe.BringIntoView();
        }

        FrameworkContentElement fce = current as FrameworkContentElement; 
        if (fce != null)
        { 
            fce.BringIntoView(); 
        }
    } 

/*
    /// 
    // 

 
 

 



 

 
 

 



 

 
 

 



 

 
 

 



 

 
 

 



 

 
 

 



 

 
 

 



 

 
 

 



 

 
 

 



 

 
 

 



 

 
 

 



 

 
 

 



 

 
 

 



 

 
 

 


*/
    #endregion Public Methods 

    //----------------------------------------------------- 
    // 
    //  Public Events
    // 
    //------------------------------------------------------

    // None
 
    //-----------------------------------------------------
    // 
    //  Internal Constructors 
    //
    //----------------------------------------------------- 

    // None

    //----------------------------------------------------- 
    //
    //  Internal Properties 
    // 
    //------------------------------------------------------
 
    // None

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

    #region Internal Methods 

    internal static void AddLogicalChild(DependencyObject parent, object child)
    {
        if (child != null && parent != null) 
        {
            FrameworkElement parentFE = parent as FrameworkElement; 
            if (parentFE != null) 
            {
                parentFE.AddLogicalChild(child); 
            }
            else
            {
                FrameworkContentElement parentFCE = parent as FrameworkContentElement; 
                if (parentFCE != null)
                { 
                    parentFCE.AddLogicalChild(child); 
                }
            } 
        }
    }

    internal static void AddLogicalChild(FrameworkElement parentFE, FrameworkContentElement parentFCE, object child) 
    {
        if (child != null) 
        { 
            if (parentFE != null)
            { 
                parentFE.AddLogicalChild(child);
            }
            else if (parentFCE != null)
            { 
                parentFCE.AddLogicalChild(child);
            } 
        } 
    }
 
    internal static void RemoveLogicalChild(DependencyObject parent, object child)
    {
        if (child != null && parent != null)
        { 
            FrameworkElement parentFE = parent as FrameworkElement;
            if (parentFE != null) 
            { 
                parentFE.RemoveLogicalChild(child);
            } 
            else
            {
                FrameworkContentElement parentFCE = parent as FrameworkContentElement;
                if (parentFCE != null) 
                {
                    parentFCE.RemoveLogicalChild(child); 
                } 
            }
        } 
    }

    internal static void RemoveLogicalChild(FrameworkElement parentFE, FrameworkContentElement parentFCE, object child)
    { 
        if (child != null)
        { 
            Debug.Assert(parentFE != null || parentFCE != null, "Either parentFE or parentFCE should be non-null"); 
            if (parentFE != null)
            { 
                parentFE.RemoveLogicalChild(child);
            }
            else
            { 
                parentFCE.RemoveLogicalChild(child);
            } 
        } 
    }
 
    internal static IEnumerator GetLogicalChildren(DependencyObject current)
    {
        FrameworkElement fe = current as FrameworkElement;
        if (fe != null) 
        {
            return fe.LogicalChildren; 
        } 

        FrameworkContentElement fce = current as FrameworkContentElement; 
        if (fce != null)
        {
            return fce.LogicalChildren;
        } 

        return MS.Internal.Controls.EmptyEnumerator.Instance; 
    } 

    #endregion Internal Methods 

    //------------------------------------------------------
    //
    //  Internal Events 
    //
    //----------------------------------------------------- 
 
    // None
 
    //------------------------------------------------------
    //
    //  Private Classes
    // 
    //-----------------------------------------------------
 
    private class EnumeratorWrapper : IEnumerable 
    {
        public EnumeratorWrapper(IEnumerator enumerator) 
        {
            if (enumerator != null)
            {
                _enumerator = enumerator; 
            }
            else 
            { 
                _enumerator = MS.Internal.Controls.EmptyEnumerator.Instance;
            } 
        }

        IEnumerator IEnumerable.GetEnumerator()
        { 
            return _enumerator;
        } 
 
        IEnumerator _enumerator;
 

        internal static EnumeratorWrapper Empty
        {
            get 
            {
                if (_emptyInstance == null) 
                { 
                    _emptyInstance = new EnumeratorWrapper(null);
                } 

                return _emptyInstance;
            }
        } 

        static EnumeratorWrapper _emptyInstance; 
    } 
}
} 

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

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