WPF - c#:这个元素目前与任何上下文无关。

I have a WPF UserControl, which I use in a WinForms Control within an ElementHostControl. Then I start a WPF Window, while the Windows Form is still open. If I then close the WPF Window, and try to add a Child Element to my WPF UserControl, it crashes at "InitializeComponent()" (of the Child Element) with the exception:I have a WPF UserControl, which I use in a WinF