c#：拖动功能

需求：放在图层上一个图片，要实现鼠标可以选中，并实现拖放功能。

代码实现：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace workflowPro
{
    public partial class Form1 : Form
    {
        private int offsetX = 0;
        private int offsetY = 0;

        public List<Control> panelControls = new List<Control>();
        public Dictionary<Control, List<List<Point>>> rules = new Dictionary<Control, List<List<Point>>>();

        public Form1()
        {
            InitializeComponent();

            PictureBox pictureBox = new PictureBox();
            pictureBox.Image = System.Drawing.Bitmap.FromFile(AppDomain.CurrentDomain.BaseDirectory + "\\201208241209467792.png");
            pictureBox.Height = 80;
            pictureBox.Width = 80;

            pictureBox.MouseDown += mouseDown;
            pictureBox.MouseUp += mouseUp;
            pictureBox.MouseMove += mouseMove;

            panelControls.Add(pictureBox);

            offsetX = this.panel1.Location.X;
            offsetY = this.panel1.Location.Y;

            this.panel1.Controls.Add(pictureBox);
        }

        private Point mouseDownPoint = new Point();
        private Control selectedControl = new Control();
        private Control moveToControl = new Control();

        void mouseDown(object sender, MouseEventArgs e)
        {
            this.selectedControl = sender as Control;

            if (e.Button == System.Windows.Forms.MouseButtons.Left)
            {
                this.lblPosition.Text = "(" + e.X + "," + e.Y + ")|";

                mouseDownPoint = e.Location;
            }
        }

        void mouseMove(object sender, MouseEventArgs e)
        {
            if (e.Button == System.Windows.Forms.MouseButtons.Left && this.selectedControl != null)
            {
                Point point = this.PointToClient(this.selectedControl.PointToScreen(new Point(e.X - mouseDownPoint.X, e.Y - mouseDownPoint.Y)));
                this.selectedControl.Location = point;
                this.selectedControl.Location.Offset(offsetX, -offsetY);

                this.lblPosition.Text = "|(" + point.X + "," + point.Y + ")";
            }
        }

        void mouseUp(object sender, MouseEventArgs e)
        {
            this.selectedControl = null;
        }

        private void MoveToWho(MouseEventArgs e)
        {
            foreach (Control control in panelControls)
            {
                int x1 = control.Location.X + offsetX;
                int y1 = control.Location.Y + offsetY;
                int x2 = x1 + control.Width;
                int y2 = y1 + control.Height;

                if (e.X > x1 && e.X < x2 && e.Y > y1 && e.Y < y2)
                {
                    this.moveToControl = control;
                }
            }
        }
    }
}