how to dock a windows form into ppt application window

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C#

hai ,
I have to dock a windows form into ppt application window. I try to do this
by using this code

PowerPoint.Presentation presentation = Globals.ThisAddIn.Application.ActivePresentation;
           MyForm.Parent =(System.Windows.Forms.Control) presentation .Parent;

then the following error message shown

"Unable to cast COM object of type 'System.__ComObject' to class type 'System.Windows.Forms.Control'. Instances of types that represent COM components cannot be cast to types that do not represent COM components; however they can be cast to interfaces as long as the underlying COM component supports QueryInterface calls for the IID of the interface."

is there is any way to solve this problem?

Thanks.