用C#窗体编程实现的简单的交互绘图程序，含绘制直线、矩形、椭圆等功能，并可以通过颜色公用对话框选择笔和实心刷的颜色-Programming with C# form a simple interactive drawing program, with drawing lines, rectangles, ellipses and other functions, and can choose the color common dialog box, pen and brush the color