C＃WPF错误指定的Visual已经是另一个Visual的子项或CompositionTarget的根 [英] C# WPF error Specified Visual is already a child of another Visual or the root of a CompositionTarget

问题描述

好的，这是一个相当常见的错误，我知道基本上我在画布上添加了两次相同的路径。



问题是我有一个虚拟路径（让我们称之为pathDummy），它会在任何时候改变它的几何形状（即它的一组点）时多次添加到画布。这就是我必须处理的方法，并且不能一直删除它。



所以我尝试通过执行以下操作从pathDummy创建一条新路径：



System.Windows.Shapes.Path newPath = SelectedPath;

paths.Add（newPath）;

plotCanvas。 Children.Add（路径[paths.Count - 1]）;



但这并没有解决问题。那么什么是在newPath中保持不变并生成错误？ thanx任何帮助

解决方案

您还没有从所选路径创建新路径;您刚刚将所选路径存储在一个新变量中。这给了你两个变量来查看同一个类的实例，而不是两个类的实例。



创建的新实例路径类，您需要使用 new 关键字来创建新实例，并复制相关属性：

  var  newPath =  new  System.Windows.Shapes.Path 
 {
 Data = SelectedPath.Data，
 Fill = SelectedPath.Fill，
 Stroke = SelectedPath.Stroke，
 ... 
}; 

Ok this is a fairly common error and I'm aware that basically I'm adding twice the same path to the canvas.

The problem is that I have a "dummy path" (let's call it pathDummy) which is added several times to the canvas any time changing it's geometry (that is its set of points). This is how I have to deal with it and can't remove it all the times.

So I tried to make a new path from pathDummy by doing:

System.Windows.Shapes.Path newPath = SelectedPath;
paths.Add(newPath);
plotCanvas.Children.Add(paths[paths.Count - 1]);

but that didn't solve the problem. So what is that stays the same in newPath and generates the error? thanx for any help

解决方案

You haven't created a new path from the selected path; you've just stored the selected path in a new variable. That gives you two variables looking at the same instance of the class, not two instances of the class.

To create a new instance of the Path class, you need to use the new keyword to create a new instance, and copy over the relevant properties:

var newPath = new System.Windows.Shapes.Path
{
    Data = SelectedPath.Data,
    Fill = SelectedPath.Fill,
    Stroke = SelectedPath.Stroke,
    ...
};

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