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yourForm.Show(System.Windows.Forms.Control.FromHandle((IntPtr)m_application.hWnd));
yourForm.Show(System.Windows.Forms.Control.FromHandle((IntPtr)m_application.hWnd));
yourForm.Show(System.Windows.Forms.Control.FromHandle(CType(m_application.hWnd, IntPtr)))
MyFormInstanceName.Show(System.Windows.Forms.Control.FromHandle(My.ArcMap.Application.hWnd))