c#语言编写的窗体画板程序。可画圆、画方、任意多边形以及铅笔、橡皮擦的功能。鼠标放入图形内变色，图形可拖曳、保存、打开。-c# language form Sketchpad program. Can draw a circle, painting party, arbitrary polygon and a pencil, eraser function. Mouse into the graphics inside color, graphics, draggable, save, open