static extern int SetWindowRgn(IntPtr hWnd, IntPtr hRgn, bool bRedraw);

Public Function SetWindowRgn(ByVal hWnd As Long, ByVal hRgn As IntPtr, ByVal bRedraw As Boolean) As Long

static extern int SetWindowRgn(IntPtr hWnd, IntPtr hRgn, bool bRedraw);

SetWindowRgn (this.Handle, CreateRoundRectRgn ( 0, 0, 562, 257, 20, 20 ),true);

    /// To achieve transparency without these restrictions, use the SetWindowRgn function.

    ''' To achieve transparency without these restrictions, use the SetWindowRgn function.

    /// To achieve transparency without these restrictions, use the SetWindowRgn function.

    ''' To achieve transparency without these restrictions, use the SetWindowRgn function.

    static extern System.UInt16  SetWindowRgn(IntPtr hWnd, IntPtr hRgn, bool bRedraw);

            SetWindowRgn(this.Handle,r3,true);

    int iRes = SetWindowRgn(this.Handle, forma, true);