C#写的绘图板，功能还不错。实现了直线，矩形，圆形，填充矩形，填充圆形。可拖动图形位置，可改变矩形大小，可放大缩小-Written by C# the drawing board, function is also good. Achieve the line, rectangle, circle, filled rectangle, the filled circle. You can drag the graphic location, you can change the rectangl