c# 子窗体居中父窗体

1.设置CenterParent不管用。只好用代码控制。  

   frmRunning_ = new FrmRunning();           
            frmRunning_.StartPosition = FormStartPosition.Manual;
            frmRunning_.Location = new Point(this.Location.X + this.Width / 2 - frmRunning_.Width / 2, this.Location.Y + this.Height / 2 - frmRunning_.Height / 2);