public partial class LoginForm : Form
    {
        private const int WM_NCHITTEST = 0x0084;
        private const int HTCAPTION = 0x0002;

protected override void WndProc(ref Message m)
        {
            switch (m.Msg)
            {
                case WM_NCHITTEST:
                    m.Result = (IntPtr)HTCAPTION;     //模拟标题栏,移动或双击可以最大或最小化窗体 

                    break;
                default:
                    base.WndProc(ref m);
                    break;
            }
        }