BUTTON在界面上位置的移动

private Point mousePos;　　//mouse＿位置＿記録
private bool beginmove=false;    //移動＿かどうか＿記録

private void button1_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
  {
   if(beginmove)
   {
    int diffx,diffy;
    diffx =  mousePos.X - e.X;
    diffy =  mousePos.Y - e.Y;
    this.button1.Location = new Point(button1.Location.X-diffx,button1.Location.Y-diffy);//buttonの位置変化
   }  
  }

  private void button1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
  {
   beginmove=true;//移動始め
   mousePos=new Point(e.X,e.Y);
  }

  private void button1_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e)
  {
      beginmove = false;//移動終わり
  }