C# 按住鼠标左键移动窗体Form的位置,C#拖动窗体通用类

private void frmLogin_Load(object sender, EventArgs e)
{
  //使用方法：在窗体的Load事件调用
   FormDragDrop.Handle(this);    
}

/// <summary>
/// 拖动鼠标移动窗体Form通用类
/// </summary>
public class FormDragDrop
{
  private Point _MouseOffset;
  private bool _IsMouseDown = false;
  private Form _form;
  
  private FormDragDrop(Form form)
  {
    _form = form;
  }
  
  /// <summary>
  /// 使用方法
  /// </summary>
  /// <param name="form"></param>
   public static void Handle(Form form)
  {
    FormDragDrop F = new FormDragDrop(form);
    F.HandleEvents();
  }
  
  private void HandleEvents()
  {
    _form.MouseDown += On_MouseDown;
    _form.MouseMove += On_MouseMove;
    _form.MouseUp += On_MouseUp;
  }
  
  private void On_MouseDown(object sender, MouseEventArgs e)
  {
    int xOffset;
    int yOffset;
    
    if (e.Button == MouseButtons.Left)
    {
      xOffset = -e.X;
      yOffset = -e.Y;
      _MouseOffset = new Point(xOffset, yOffset);
      _IsMouseDown = true;
    }
  }
  
  private void On_MouseMove(object sender, MouseEventArgs e)
  {
    if (_IsMouseDown)
    {
      Point mousePos = Control.MousePosition;
      mousePos.Offset(_MouseOffset.X, _MouseOffset.Y);
      _form.Location = mousePos;
    }
  }
  
  private void On_MouseUp(object sender, MouseEventArgs e)
  {
    if (e.Button == MouseButtons.Left)
    {
      _IsMouseDown = false;
    }
  }
  
}