我就想知道怎么实现。。。（事件和方法）
本帖最后由 u011311854 于 2013-10-04 20:52:16 编辑

public partial class Form1 : Form
    {
       Point pt;
       public bool a ;
 
        public Form1()
        {
            InitializeComponent();
             
        }
 
        private void panel1_Paint(object sender, PaintEventArgs e)
        {
          if (a==true)
          {
           Graphics dc = e.Graphics;
           Pen blue = new Pen(Color.Blue, 3);
           dc.DrawRectangle(blue, pt.X, pt.Y, 50, 50);
            
          }
 
          a = false;
            
        }
 
        private void panel1_MouseMove(object sender, MouseEventArgs e)
        {
            a = false;
            pt.X = e.X;
            pt.Y = e.Y;
            this.Text = string.Format("鼠标位置：({0},{1})", pt.X, pt.Y);
 
        }
 
        private void panel1_MouseDown(object sender, MouseEventArgs e)
        {
            a = true;
            
        }
 
        private void panel1_MouseUp(object sender, MouseEventArgs e)
        {
            a = true;
        }

我想，鼠标抬起时，在panel上画，我想知道事件和画图的方法怎么调用。。。
这段代码，想通过a作为一个开关。但是实现不了。。。
谢谢！
[解决办法]
private?void?panel1_MouseMove(object?sender,?MouseEventArgs?e)
????????{
????????????a?=?(e.Button == == MouseButtons.Left);??
????????}

这些可以删除：
????????private?void?panel1_MouseDown(object?sender,?MouseEventArgs?e)
????????{
????????????a?=?true;
?????????????
????????}
??
????????private?void?panel1_MouseUp(object?sender,?MouseEventArgs?e)
????????{
????????????a?=?true;
????????}
[解决办法]
鼠标按下，记录起始点坐标，将标记设为true
鼠标移动，如果标记为true，则设置结束点坐标，先清空，再画上矩形
鼠标抬起，记录结束点坐标，将标记设为false

[解决办法]
a = true;
这句话下面加一句话：
Invalidate();
[解决办法]
你的鼠标点击事件本身无法触发panel的paint事件，你必须再写一句调用paint事件，可以试试 panel1.Refresh();或者直接调panel1_Paint(object sender, PaintEventArgs e)
[解决办法]

  private void panel1_Paint(object sender, PaintEventArgs e)
        {
            if (a==true)
            {
                Graphics dc = e.Graphics;
                Pen blue = new Pen(Color.Blue, 3);
                dc.DrawRectangle(blue, pt.X, pt.Y, 50, 50);
            } 
 

        }

        private void panel1_MouseDown(object sender, MouseEventArgs e)
        {
            a = false;
            this.panel1.Refresh();
        }

        private void panel1_MouseUp(object sender, MouseEventArgs e)
        {
            a = true;
            pt.X = e.X;
            pt.Y = e.Y;
            this.Text = string.Format("{0}{1}",pt.X,pt.Y);
            this.panel1.Refresh();
        }