潜移默化学会WPF（企业经验篇）--全新替代掉VisualHelper功能的类，可视树泛型查找，功能强大

/// <summary>
/// Finds a Child of a given item in the visual tree.
/// </summary>
/// <param name="parent">A direct parent of the queried item.</param>
/// <typeparam name="T">The type of the queried item.</typeparam>
/// <param name="childName">x:Name or Name of child. </param>
/// <returns>The first parent item that matches the submitted type parameter.
/// If not matching item can be found,
/// a null parent is being returned.</returns>
public static T FindChild<T>(DependencyObject parent, string childName)
where T : DependencyObject
{
// Confirm parent and childName are valid.
if (parent == null) return null;

T foundChild = null;

int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < childrenCount; i++)
{
var child = VisualTreeHelper.GetChild(parent, i);
// If the child is not of the request child type child
T childType = child as T;
if (childType == null)
{
// recursively drill down the tree
foundChild = FindChild<T>(child, childName);

// If the child is found, break so we do not overwrite the found child.
if (foundChild != null) break;
}
else if (!string.IsNullOrEmpty(childName))
{
var frameworkElement = child as FrameworkElement;
// If the child's name is set for search
if (frameworkElement != null && frameworkElement.Name == childName)
{
// if the child's name is of the request name
foundChild = (T)child;
break;
}
}
else
{
// child element found.
foundChild = (T)child;
break;
}
}

return foundChild;
}

public DependencyObject FindChild(DependencyObject o, Type childType)
{
DependencyObject foundChild = null;
if (o != null)
{
int childrenCount = VisualTreeHelper.GetChildrenCount(o);
for (int i = 0; i < childrenCount; i++)
{
var child = VisualTreeHelper.GetChild(o, i);
if (child.GetType() != childType)
{
foundChild = FindChild(child, childType);
}
else
{
foundChild = child;
break;
}
}
}
return foundChild;
}

public static T FindVisualParent<T>(UIElement element) where T : UIElement
{
UIElement parent = element; while (parent != null)
{
T correctlyTyped = parent as T; if (correctlyTyped != null)
{
return correctlyTyped;
}
parent = VisualTreeHelper.GetParent(parent) as UIElement;
} return null;
}

public static T FindChild<T>(DependencyObject parent) where T : DependencyObject
{
if (parent == null) return null;

T childElement = null; int childrenCount = VisualTreeHelper.GetChildrenCount(parent); for (int i = 0; i < childrenCount; i++)
{
var child = VisualTreeHelper.GetChild(parent, i);
T childType = child as T; if (childType == null)
{
childElement = FindChild<T>(child); if (childElement != null) break;
}
else
{
childElement = (T)child; break;
}
} return childElement;
}