Canvas has two attached properties – left and top.
You can do:
MyGroupBox.SetValue(Canvas.LeftProperty,50.0);
And similarly with topproperty where mygroupbox is your groupbox.
50 is a double and the distance in px from top or left edge of the canvas the top left corner of the goupbox is to be located.
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solved How to change the location of a groupbox programmatically [closed]