WinForm拖动没有标题栏窗体的方法

 Point _HoverTreePosition;
        public Form_HoverTree()
        {
            InitializeComponent();
            _HoverTreePosition = new Point();

        }

        /// <summary>
        /// 记录鼠标起始位置 hovertree.com
        /// </summary>
        private void Form_HoverTree_MouseDown(object sender, MouseEventArgs e)
        {
            _HoverTreePosition.X = e.X;
            _HoverTreePosition.Y = e.Y;
        }

        /// <summary>
        /// 按住左键，鼠标移动窗体跟着移动 - 何问起 
        /// </summary>
        private void Form_HoverTree_MouseMove(object sender, MouseEventArgs e)
        {
            if(e.Button== MouseButtons.Left)
            {
                Point h_myPosittion = MousePosition;
                h_myPosittion.Offset(-_HoverTreePosition.X, -_HoverTreePosition.Y);
                Location = h_myPosittion;
            }
        }