private Boolean fals = true;

         /// <summary>

         /// 单击事件

         /// </summary>

         /// <param name="sender"></param>

         /// <param name="e"></param>

         private void pictureBox3_Click(object sender, EventArgs e)

         {

             if (fals == true)

             {

                 this.pictureBox3.BackgroundImage = Image.FromFile(Application.StartupPath + "\\image\\" + "stop.ico");

                 fals = false;

             }

             else

             {

                 this.pictureBox3.BackgroundImage = Image.FromFile(Application.StartupPath + "\\image\\" + "start.ico");

                 fals = true;

             }

         }