WPF 利用视觉树获取指定名称对象、指定类型对象、以及判断是否有验证错误

1.利用视觉树获取指定名称对象

/// <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 GetChildWithName<T>(this 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 childT childType = child as T;if (childType == null){// recursively drill down the treefoundChild = GetChildWithName<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 searchif (frameworkElement != null && frameworkElement.Name == childName){// if the child's name is of the request namefoundChild = (T)child;break;}}else{// child element found.foundChild = (T)child;break;}}return foundChild;
}

2.返回指定类型的子对象

比如：在一个Grid内部有很多TextBox/ComboBox ，需要获取这个控件对象。

var children=Grid.GetChildren(new List<Type>(){ typeof(TextBox),typeof(ComboBox)});

/// <summary>
/// 返回指定类型的子对象
/// </summary>
/// <param name="p_element"></param>
/// <param name="includeTypes"></param>
/// <returns></returns>
public static IEnumerable<UIElement> GetChildren(this DependencyObject p_element, List<Type> includeTypes)
{for (int i = 0; i < VisualTreeHelper.GetChildrenCount(p_element); i++){var child = VisualTreeHelper.GetChild(p_element, i) as UIElement;if (child == null){continue;}Type type = child.GetType();if (includeTypes.Contains(type)){yield return child;}else{foreach (var c in child.GetChildren(includeTypes)){yield return c;}}}
}

3.获取UI对象（UserControl）内部是否存在验证错误

string errorMsg=string.Empty;

if(UserControl.GetChildrenValidationHasError<TextBox>(ref errorMsg))

{

        //UserControl 内部的TextBox 有验证错误

        MessageBox.Show(errorMsg);//提示错误消息

}

/// <summary>
/// 获取当前DependencyObject（含特定类型子对象）是否存在Validation错误
/// </summary>
/// <param name="p_element"></param>
/// <param name="errorMsg"></param>
/// <returns></returns>
public static bool GetChildrenValidationHasError<T>(this DependencyObject p_element, ref string errorMsg) where T : UIElement
{var children = GetChildren<T>(p_element);foreach (var child in children){if (CheckDependencyObjectHasError(child, ref errorMsg)){return true;}}return false;
}/// <summary>
/// 获取当前DependencyObject（含所有UI子对象）是否存在Validation错误
/// </summary>
/// <param name="p_element"></param>
/// <param name="errorMsg"></param>
/// <returns></returns>
public static bool GetChildrenValidationHasError(this DependencyObject p_element, List<Type> includeTypes, ref string errorMsg)
{var children = GetChildren(p_element, includeTypes);foreach (var child in children){if (CheckDependencyObjectHasError(child, ref errorMsg)){return true;}}return false;
}/// <summary>
/// 获取当前DependencyObject是否存在Validation错误
/// </summary>
/// <param name="child"></param>
/// <param name="errorMsg"></param>
/// <returns></returns>
public static bool CheckDependencyObjectHasError(this DependencyObject child, ref string errorMsg)
{if (child != null && Validation.GetHasError(child)){var errors = Validation.GetErrors(child);if (errors != null){errorMsg = string.Join("\n\r", errors.Select(m => m.ErrorContent).ToArray());}return true;}return false;
}