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 WinFormDrag{  public partial class Form1 : Form  {    //鼠標按下坐標（control控件的相對坐標）    Point mouseDownPoint = Point.Empty;    //顯示拖動效果的矩形    Rectangle rect = Rectangle.Empty;    //是否正在拖拽    bool isDrag = false;    public Form1()    {      InitializeComponent();    }    private void Form1_Paint(object sender, PaintEventArgs e)    {      if (rect != Rectangle.Empty)      {        if (isDrag)        {//畫一個和Control一樣大小的黑框          e.Graphics.DrawRectangle(Pens.Black, rect);        }        else        {          e.Graphics.DrawRectangle(new Pen(this.BackColor), rect);        }      }    }    /// <summary>    /// 按下鼠標時    /// </summary>    /// <param name="sender"></param>    /// <param name="e"></param>    private void pb1_MouseDown(object sender, MouseEventArgs e)    {      if (e.Button == MouseButtons.Left)      {        mouseDownPoint = e.Location;        //記錄控件的大小        rect = pb1.Bounds;      }    }    /// <summary>    /// 移過時    /// </summary>    /// <param name="sender"></param>    /// <param name="e"></param>    private void pb1_MouseMove(object sender, MouseEventArgs e)    {      if (e.Button == MouseButtons.Left)      {        isDrag = true;        //重新設置rect的位置，跟隨鼠標移動        rect.Location = getPointToForm(new Point(e.Location.X - mouseDownPoint.X, e.Location.Y - mouseDownPoint.Y));        this.Refresh();      }    }    /// <summary>    /// 釋放鼠標按鈕時    /// </summary>    /// <param name="sender"></param>    /// <param name="e"></param>    private void pb1_MouseUp(object sender, MouseEventArgs e)    {      if (e.Button == MouseButtons.Left)      {        if (isDrag)        {          isDrag = false;          //移動control到放開鼠標的地方          pb1.Location = rect.Location;          this.Refresh();        }        reset();      }    }    //重置變量    private void reset()    {      mouseDownPoint = Point.Empty;      rect = Rectangle.Empty;      isDrag = false;    }    //把相對與control控件的坐標，轉換成相對于窗體的坐標。    private Point getPointToForm(Point p)    {      return this.PointToClient(pb1.PointToScreen(p));    }  }}