Win32.UpdateWindow(hwnd);

static extern bool UpdateWindow(IntPtr hWnd);

Private Shared Function UpdateWindow(ByVal hWnd As IntPtr) As Boolean

Public Declare Function UpdateWindow Lib "user32" (ByVal hWnd As Long) As Long

    /// The WM_PAINT message is sent when the system or another application makes a request to paint a portion of an application's window. The message is sent when the UpdateWindow or RedrawWindow function is called, or by the DispatchMessage function when the application obtains a WM_PAINT message by using the GetMessage or PeekMessage function.