在C#中使用组合框数据绑定的问题

在C#中使用数据绑定后例如：
   private void InitCombo()
        {
            this.cobRoomTypeName.DataSource = RoomTypeManager.GetAllRoomType();
            this.cobRoomTypeName.DisplayMember = "TypeName";
            this.cobRoomTypeName.ValueMember = "TypeID";
        }
绑定组合框。
那么当进行绑定的时候，会自动触发SelectedIndexChange事件。
那么如果定义如下方法：
        private void cobRoomTypeName_SelectedIndexChanged(object sender, EventArgs e)
       {
           if (this.cobRoomTypeName.SelectedValue != null)
           {
               int typeId = Convert.ToInt32(this.cobRoomTypeName.SelectedValue);
               RoomType rt = RoomTypeManager.GetRoomTypeByTypeId(typeId);
               this.txtPrice.Text = rt.TypePrice + "";
           }
        }
想要获取选择的Value属性，就会出错，应该如下处理：
        /// <summary>
        /// 使用这个事件可以在修改组合框内容的时候修改价格
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void cobRoomTypeName_SelectionChangeCommitted(object sender, EventArgs e)
        {
            if (this.cobRoomTypeName.SelectedValue != null)
            {
                int typeId = Convert.ToInt32(this.cobRoomTypeName.SelectedValue);
                RoomType rt = RoomTypeManager.GetRoomTypeByTypeId(typeId);
                this.txtPrice.Text = rt.TypePrice + "";
            }
        }