通过标记去除帆布子（

Question

）

我有一个椭圆（前导），我想通过标记（“p”）从帆布（canvas1）中删除。 我想这一点，但它不工作：

var child = (from c in canvas1.Children 
      where "p".Equals(c.Tag) 
      select c).First(); 
canvas1.Children.Remove(child); 

它给了我这个错误：

"Could not find an implementation of the query pattern for source type 'System.Windows.Controls.UIElementCollection'. 'Where' not found. Consider explicitly specifying the type of the range variable 'c'."

我怎么能按标签删除canvas孩子？

Answer 1

的UIElementCollection实现普通的旧IEnumerable，因此是不是默认与LINQ兼容。您需要查询

var child = (from c in canvas1.Children.Cast<FrameworkElement>() 
      where "p".Equals(c.Tag) 
      select c).First(); 
canvas1.Children.Remove(child); 

注意，这个代码是suspectible运行时错误如果在集合（的UIElement另一个派生）在非FrameworkElement之前将它转换成一个强类型IEnumerable<T>。为了防止这种情况，你可能最好去OfType方法

var child = (from c in canvas1.Children.OfType<FrameworkElement>() 
      where "p".Equals(c.Tag) 
      select c).First(); 
canvas1.Children.Remove(child); 

Answer 2

var child = (from FrameworkElement c in canvas1.Children 
      where "p".Equals(c.Tag) 
      select c).First(); 
canvas1.Children.Remove(child); 

或

var child = (from c in canvas1.Children.Cast<FrameworkElement>() 
      where "p".Equals(c.Tag) 
      select c).First(); 
canvas1.Children.Remove(child);