我需要在WPF控件层次结构中搜索与给定名称或类型匹配的控件。我该怎么做呢?


当前回答

我有一个这样的序列函数(这是完全一般的):

    public static IEnumerable<T> SelectAllRecursively<T>(this IEnumerable<T> items, Func<T, IEnumerable<T>> func)
    {
        return (items ?? Enumerable.Empty<T>()).SelectMany(o => new[] { o }.Concat(SelectAllRecursively(func(o), func)));
    }

有直系子女:

    public static IEnumerable<DependencyObject> FindChildren(this DependencyObject obj)
    {
        return Enumerable.Range(0, VisualTreeHelper.GetChildrenCount(obj))
            .Select(i => VisualTreeHelper.GetChild(obj, i));
    }

在树中找到所有的子节点:

    public static IEnumerable<DependencyObject> FindAllChildren(this DependencyObject obj)
    {
        return obj.FindChildren().SelectAllRecursively(o => o.FindChildren());
    }

你可以在Window上调用这个来获得所有的控件。

在你有集合之后,你可以使用LINQ(即OfType, Where)。

其他回答

虽然我一般喜欢递归,但在c#中编程时,它不如迭代有效,所以也许下面的解决方案比John Myczek建议的更整洁?这将从给定控件搜索层次结构,以查找特定类型的祖先控件。

public static T FindVisualAncestorOfType<T>(this DependencyObject Elt)
    where T : DependencyObject
{
    for (DependencyObject parent = VisualTreeHelper.GetParent(Elt);
        parent != null; parent = VisualTreeHelper.GetParent(parent))
    {
        T result = parent as T;
        if (result != null)
            return result;
    }
    return null;
}

像这样调用它来找到包含一个名为ExampleTextBox的控件的窗口:

Window window = ExampleTextBox.FindVisualAncestorOfType<Window>();

要从代码中找到给定类型的祖先,您可以使用:

[CanBeNull]
public static T FindAncestor<T>(DependencyObject d) where T : DependencyObject
{
    while (true)
    {
        d = VisualTreeHelper.GetParent(d);

        if (d == null)
            return null;

        var t = d as T;

        if (t != null)
            return t;
    }
}

这个实现使用迭代而不是递归,可以稍微快一点。

如果你使用的是c# 7,这段代码可以略短:

[CanBeNull]
public static T FindAncestor<T>(DependencyObject d) where T : DependencyObject
{
    while (true)
    {
        d = VisualTreeHelper.GetParent(d);

        if (d == null)
            return null;

        if (d is T t)
            return t;
    }
}

您可以使用VisualTreeHelper来查找控件。下面是一个使用VisualTreeHelper查找指定类型的父控件的方法。您也可以使用VisualTreeHelper以其他方式查找控件。

public static class UIHelper
{
   /// <summary>
   /// Finds a parent of a given item on the visual tree.
   /// </summary>
   /// <typeparam name="T">The type of the queried item.</typeparam>
   /// <param name="child">A direct or indirect child of the queried item.</param>
   /// <returns>The first parent item that matches the submitted type parameter. 
   /// If not matching item can be found, a null reference is being returned.</returns>
   public static T FindVisualParent<T>(DependencyObject child)
     where T : DependencyObject
   {
      // get parent item
      DependencyObject parentObject = VisualTreeHelper.GetParent(child);

      // we’ve reached the end of the tree
      if (parentObject == null) return null;

      // check if the parent matches the type we’re looking for
      T parent = parentObject as T;
      if (parent != null)
      {
         return parent;
      }
      else
      {
         // use recursion to proceed with next level
         return FindVisualParent<T>(parentObject);
      }
   }
}

这样叫它:

Window owner = UIHelper.FindVisualParent<Window>(myControl);

下面是一个使用灵活谓词的解决方案:

public static DependencyObject FindChild(DependencyObject parent, Func<DependencyObject, bool> predicate)
{
    if (parent == null) return null;

    int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
    for (int i = 0; i < childrenCount; i++)
    {
        var child = VisualTreeHelper.GetChild(parent, i);

        if (predicate(child))
        {
            return child;
        }
        else
        {
            var foundChild = FindChild(child, predicate);
            if (foundChild != null)
                return foundChild;
        }
    }

    return null;
}

例如,你可以这样称呼它:

var child = FindChild(parent, child =>
{
    var textBlock = child as TextBlock;
    if (textBlock != null && textBlock.Name == "MyTextBlock")
        return true;
    else
        return false;
}) as TextBlock;

这将消除一些元素-您应该像这样扩展它,以支持更广泛的控件数组。简单的讨论,请看这里

 /// <summary>
 /// Helper methods for UI-related tasks.
 /// </summary>
 public static class UIHelper
 {
   /// <summary>
   /// Finds a parent of a given item on the visual tree.
   /// </summary>
   /// <typeparam name="T">The type of the queried item.</typeparam>
   /// <param name="child">A direct or indirect child of the
   /// queried item.</param>
   /// <returns>The first parent item that matches the submitted
   /// type parameter. If not matching item can be found, a null
   /// reference is being returned.</returns>
   public static T TryFindParent<T>(DependencyObject child)
     where T : DependencyObject
   {
     //get parent item
     DependencyObject parentObject = GetParentObject(child);

     //we've reached the end of the tree
     if (parentObject == null) return null;

     //check if the parent matches the type we're looking for
     T parent = parentObject as T;
     if (parent != null)
     {
       return parent;
     }
     else
     {
       //use recursion to proceed with next level
       return TryFindParent<T>(parentObject);
     }
   }

   /// <summary>
   /// This method is an alternative to WPF's
   /// <see cref="VisualTreeHelper.GetParent"/> method, which also
   /// supports content elements. Do note, that for content element,
   /// this method falls back to the logical tree of the element!
   /// </summary>
   /// <param name="child">The item to be processed.</param>
   /// <returns>The submitted item's parent, if available. Otherwise
   /// null.</returns>
   public static DependencyObject GetParentObject(DependencyObject child)
   {
     if (child == null) return null;
     ContentElement contentElement = child as ContentElement;

     if (contentElement != null)
     {
       DependencyObject parent = ContentOperations.GetParent(contentElement);
       if (parent != null) return parent;

       FrameworkContentElement fce = contentElement as FrameworkContentElement;
       return fce != null ? fce.Parent : null;
     }

     //if it's not a ContentElement, rely on VisualTreeHelper
     return VisualTreeHelper.GetParent(child);
   }
}