c# 改變Mdi表單區背景樣式

代碼
        /// <summary>
        /// 更改Mdi背景樣式
        /// </summary>
        private void ChangeMidBackStyle()
        {
            //更改Mdi背景樣式
            MdiClient mctMdi = new MdiClient();
            foreach (Control conMid in this.Controls)
            {
                //得到Mdi
                if (conMid.GetType().ToString() == "System.Windows.Forms.MdiClient")
                {
                    mctMdi = (System.Windows.Forms.MdiClient)conMid;
                    //改變背景顏色
                    mctMdi.BackColor = Color.FromArgb(238, 243, 250);
                    if (File.Exists("img/ContextMenu/Back.png"))
                    {
                        //改變背景圖片排列
                        this.BackgroundImageLayout = ImageLayout.Center;
                        //改變背景圖片
                        mctMdi.BackgroundImage = Image.FromFile(@"img\ContextMenu\Back.png");
                    }
                    break;
                }
            }
        }