C# Signature:

[DllImport("user32.dll")]
static extern bool RedrawWindow(IntPtr hWnd, [In] ref RECT lprcUpdate,
   IntPtr hrgnUpdate, uint flags);

[DllImport("user32.dll")]
static extern bool RedrawWindow(IntPtr hWnd, IntPtr lprcUpdate,
                  IntPtr hrgnUpdate, uint flags);

User-Defined Types:

None.

Notes:

RedrawWindow() flags:

#define RDW_INVALIDATE      0x0001
#define RDW_INTERNALPAINT   0x0002
#define RDW_ERASE           0x0004

#define RDW_VALIDATE        0x0008
#define RDW_NOINTERNALPAINT 0x0010
#define RDW_NOERASE         0x0020

#define RDW_NOCHILDREN      0x0040
#define RDW_ALLCHILDREN     0x0080

#define RDW_UPDATENOW       0x0100
#define RDW_ERASENOW        0x0200

#define RDW_FRAME           0x0400
#define RDW_NOFRAME         0x0800

[StructLayout(LayoutKind.Sequential)]
public struct RECT {
     public int Left;
     public int Top;
     public int Right;
     public int Bottom;
}

Tips & Tricks:

Please add some!

Sample Code:

    private void InvalidateWindow()
    {
        WinAPI.RedrawWindow(this.Handle, IntPtr.Zero, IntPtr.Zero,
         0x0400/*RDW_FRAME*/ | 0x0100/*RDW_UPDATENOW*/
         | 0x0001/*RDW_INVALIDATE*/);
    }

Alternative Managed API:

Do you know one? Please contribute it!