如何去除MDI父窗体下子窗体的标题栏

实现代码：

FormSearch childForm = new FormSearch();
childForm.MdiParent = this;
childForm.FormBorderStyle = FormBorderStyle.None;
childForm.ControlBox = false;
childForm.MaximizeBox = false;
childForm.MinimizeBox = false;
childForm.Show();
childForm.Dock = DockStyle.Fill;