public partial class Form1 : Form{  /*   * 理解了下面的幾個概念,就能完全明白相對坐標的變化.   * MouseEventArgs e 為事件鼠標參數,因此,e.Location 指示了位于事件源上的光標坐標   * Cursor.Position 獲取的是相對于用戶屏幕的光標坐標   * PointToClient() 方法可將屏幕坐標 Cursor.Position 換算成工作區的坐標   * 因此,換算后的 Cursor.Position 減去 e.Location 得到的始終是事件源的 Location  */  /// <summary>  /// 鼠標按下為true  /// </summary>  private bool Mousedown;  /// <summary>  /// 鼠標在事件源的位置  /// </summary>  private int CurX = 0;  private int CurY = 0;  public Form1()  {    InitializeComponent();  }  private void Controls_MouseDown(object sender, MouseEventArgs e)  {    CurX = e.X;    CurY = e.Y;    Mousedown = true;    if (sender is TextBox)    {      ((TextBox)sender).Cursor = Cursors.Arrow;    }  }  private void Controls_MouseMove(object sender, MouseEventArgs e)  {    if (Mousedown)    {      // 獲取當前屏幕的光標坐標       Point pTemp = new Point(Cursor.Position.X, Cursor.Position.Y);      // 轉換成工作區坐標       pTemp = this.PointToClient(pTemp);      // 定位事件源的 Location      Control control = sender as Control;      control.Location = new Point(pTemp.X - CurX, pTemp.Y - CurY);            }  }  private void Controls_MouseUp(object sender, MouseEventArgs e)  {    Mousedown = false;    if (sender is TextBox)    {      ((TextBox)sender).Cursor = Cursors.IBeam;    }  }}