C# WPF error Specified Visual is already a child of another Visual or the root of a CompositionTarget

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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

Posted 3-Sep-15 5:27am

Patrick70__

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Richard Deeming · Accepted Answer · 2015-09-03T06:25:00

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:

C#

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