如何使MDI窗体只显示当前点击Form

private void toolStripUser_Click(object sender, EventArgs e)
        {
            if (this.MdiChildren.Length > 0) this.MdiChildren[0].Close();
            SetSystem.frmUser frmuser = new SetSystem.frmUser();
            frmuser.MdiParent = this;
            frmuser.Show();
        }