Drowing and Delaying

Question

I have such as a cod, it should be wait for 3second, and then drow line, and repeat all this 4 times, but it waits 12 second(3x4) and the drows 4 lines at onse. what is the problem?? ////////////////////////////////////////////////////////////////////////////////// Pen myPen = new Pen(System.Drawing.Color.Red, 1); for (int ii = 0; ii <= 3; ii++) { Thread.Sleep(3000); //????? ?? 3 ??????? graphDrawingAxis.DrawLine(myPen, ii*200, 350, 200, 120); } /////////////////////////////////////////////////////////////////////////////