实现效果：
知识运用：
Graphics类的DrawLine方法和MouseEventArgs类的x,y属性
实现代码：
private void Form1_MouseMove(object sender, MouseEventArgs e)
{
if (lastPoint.Equals(Point.Empty)) //判断绘图开始点是否为空
{
lastPoint = new Point(e.X,e.Y); //记录鼠标当前位置
}
if (onMouseDown) //开始绘图
{
graphics = this.CreateGraphics();
Point currPoint = new Point(e.X, e.Y); //获取鼠标当前位置
graphics.DrawLine(new Pen (Color.Black),lastPoint,currPoint); //绘图
}
lastPoint = new Point(e.X,e.Y); //更新绘图点
}
private void Form1_MouseDown(object sender, MouseEventArgs e)
{
onMouseDown = true; //开始绘图标识设为true;
}
private void Form1_MouseUp(object sender, MouseEventArgs e)
{
onMouseDown = false; //开始绘图标识设为false;
}
