protected override void OnMouseDown(System.Windows.Forms.MouseEventArgs e) { isMouseDown = true; base.OnMouseDown(e); appCanvas.Resize(e.X, -e.Y); IntPtr hwnd = this.Handle; IntPtr hdc = WinNative.GetDC(hwnd); //canvas paint, clear bg appCanvas.RenderTo(hdc); WinNative.ReleaseDC(hwnd, hdc); }