int x, y;
        bool mousedown=false;

        private void button1_Click(object sender, EventArgs e)
        {
            PictureBox pic = new PictureBox();
            pic.Image = Image.FromFile("c:\\1.bmp");
            pic.Parent = this;
            pic.MouseDown += new MouseEventHandler
                (
                delegate(object obj, MouseEventArgs ex)
                {
                    if (ex.Button == MouseButtons.Left)
                    {
                        x = ex.X;
                        y = ex.Y;
                        mousedown = true;
                    }
                }
                );
            pic.MouseUp += new MouseEventHandler
                (
                delegate(object obj, MouseEventArgs ex)
                {
                    mousedown = false;
                }
                );
            pic.MouseMove += new MouseEventHandler
                (
                delegate(object obj, MouseEventArgs ex)
                {
                    if (mousedown)
                    {
                        ((PictureBox)obj).Left += ex.X - x;
                        ((PictureBox)obj).Top += ex.Y - y;
                    }
                }
                );
        }

------解决方案--------------------
 public partial class Form1 : Form
   {
       public Form1()
       {
           InitializeComponent();
       }

       private void Form1_Load(object sender, EventArgs e)
       {

       }
       System.Collections.Generic.List<mouselocation> mouse = new List<mouselocation>();
       protected override void OnMouseMove(MouseEventArgs e)
       {
           if (flag)
           {
               mouselocation ms = new mouselocation();
               ms.x = e.X;
               ms.y = e.Y;
               mouse.Add(ms);
           }
           Grap();
           base.OnMouseMove(e);
       }

       private void Grap()
       {
           //  Refresh();
           Graphics gp = this.CreateGraphics();
           Brush bsh = new SolidBrush(Color.Red);
           Pen p = new Pen(bsh);
           for (int i = 0; i < mouse.Count-1; i++)
           {
               gp.DrawLine(p,mouse[i].x,mouse[i].y,mouse[i+1].x,mouse[i+1].y);
           }
       }
       public bool flag = false;
       private void button1_Click(object sender, Event