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【】 WPF 页面控件找到子孙控件
作者:dezai / 发布于2014/3/11/ 581
WPF 页面控件找到子孙控件
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Media;
using System.Windows.Media.Media3D;

namespace Gishu.WPF.Utilities
{
static class DependencyObjExtensions
{
/// <summary>
/// Find the first child of the specified type (the child must exist)
/// by walking down the logical/visual trees
/// Will throw an exception if a matching child does not exist. If you're not sure, use the TryFindChild method instead.
/// </summary>
/// <typeparam name="T">The type of child you want to find</typeparam>
/// <param name="parent">The dependency object whose children you wish to scan</param>
/// <returns>The first descendant of the specified type</returns>
/// <remarks> usage: myWindow.FindChild<StackPanel>() </StackPanel></remarks>
public static T FindChild<T>(this DependencyObject parent)
where T : DependencyObject
{
return parent.FindChild<T>(child => true);
}

/// <summary>
/// Find the first child of the specified type (the child must exist)
/// by walking down the logical/visual trees, which meets the specified criteria
/// Will throw an exception if a matching child does not exist. If you're not sure, use the TryFindChild method instead.
/// </summary>
/// <typeparam name="T">The type of child you want to find</typeparam>
/// <param name="parent">The dependency object whose children you wish to scan</param>
/// <param name="predicate">The child object is selected if the predicate evaluates to true</param>
/// <returns>The first matching descendant of the specified type</returns>
/// <remarks> usage: myWindow.FindChild<StackPanel>( child => child.Name == "myPanel" ) </StackPanel></remarks>
public static T FindChild<T>(this DependencyObject parent, Func<T, bool> predicate)
where T : DependencyObject
{
return parent.FindChildren<T>(predicate).First();
}

/// <summary>
/// Use this overload if the child you're looking may not exist.
/// </summary>
/// <typeparam name="T">The type of child you're looking for</typeparam>
/// <param name="parent">The dependency object whose children you wish to scan</param>
/// <param name="foundChild">out param - the found child dependencyobject, null if the method returns false</param>
/// <returns>True if a child was found, else false</returns>
public static bool TryFindChild<T>(this DependencyObject parent, out T foundChild)
where T : DependencyObject
{
return parent.TryFindChild<T>(child => true, out foundChild);
}

/// <summary>
/// Use this overload if the child you're looking may not exist.
/// </summary>
/// <typeparam name="T">The type of child you're looking for</typeparam>
/// <param name="parent">The dependency object whose children you wish to scan</param>
/// <param name="predicate">The child object is selected if the predicate evaluates to true</param>
/// <param name="foundChild">out param - the found child dependencyobject, null if the method returns false</param>
/// <returns>True if a child was found, else false</returns>
public static bool TryFindChild<T>(this DependencyObject parent, Func<T, bool> predicate, out T foundChild)
where T : DependencyObject
{
foundChild = null;
var results = parent.FindChildren<T>(predicate);
if (results.Count() == 0)
return false;

foundChild = results.First();
return true;
}

/// <summary>
/// Get a list of descendant dependencyobjects of the specified type and which meet the criteria
/// as specified by the predicate
/// </summary>
/// <typeparam name="T">The type of child you want to find</typeparam>
/// <param name="parent">The dependency object whose children you wish to scan</param>
/// <param name="predicate">The child object is selected if the predicate evaluates to true</param>
/// <returns>The first matching descendant of the specified type</returns>
/// <remarks> usage: myWindow.FindChildren<StackPanel>( child => child.Name == "myPanel" ) </StackPanel></remarks>
public static IEnumerable<T> FindChildren<T>(this DependencyObject parent, Func<T, bool> predicate)
where T : DependencyObject
{
var children = newList<DependencyObject>();

if ((parent is Visual) || (parent is Visual3D))
{
var visualChildrenCount = VisualTreeHelper.GetChildrenCount(parent);
for (int childIndex = 0; childIndex < visualChildrenCount; childIndex++)
children.Add(VisualTreeHelper.GetChild(parent, childIndex));
}
foreach (var logicalChild in LogicalTreeHelper.GetChildren(parent).OfType<DependencyObject>())
if (!children.Contains(logicalChild))
children.Add(logicalChild);

foreach (var child in children)
{
var typedChild = child as T;
if ((typedChild != null) && predicate.Invoke(typedChild))
yield return typedChild;

foreach (var foundDescendant in FindChildren(child, predicate))
yield return foundDescendant;
}
yield break;
}
}
}
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