vb环境下实现画线画矩形，交互式操作，模仿cad共功能-vb environment drawing a line under the rectangular painting, interactive operation, a total functional mimic cad

在vb中实现交互式画图，绘制简单2维图形，窗体中点击显示，可改变颜色，线条样式-Implement in vb interactive drawing, draw a simple two-dimensional graphics, forms, click on display, can change the color, line styles