DataGridView 在下拉框添加下来事件

DataGridView中有一种下拉框式的列，给这个列添加下拉事件时需要转化一下才可以绑定下拉事件

/// <summary>
/// 服务类型
/// </summary>
DataGridViewComboBoxEditingControl cboServiceType = null;

#region 维修项目 服务类型 下拉框 事件
        /// <summary>
        /// 设置下拉框值改变时的处理
        /// 作者“；李德彦
        /// 时间：2015年12月7日
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void dgv_tb_maintain_three_guaranty_item_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            try
            {
                if (dgv_tb_maintain_three_guaranty_item.CurrentCell.OwningColumn == dgv_cbx1_WORK_SERVICE_TYPE)
                {
                    cboServiceType = (DataGridViewComboBoxEditingControl)e.Control;
                    cboServiceType.SelectedIndexChanged += new EventHandler(cboServiceType_SelectedIndexChanged);
                }
            }
            catch (Exception ex)
            {
                GlobalStaticObj.GlobalLogService.WriteLog(LocalOperation.GetStringByKey("sanbaofuwudantianjiamingxiyichang", "三包服务单，添加明细事件异常：") + ex.Message);
            }

        }
        /// <summary>
        /// 服务类型改变事件
        /// 作者：李德彦
        /// 时间：2015年12月7日
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void cboServiceType_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (cboServiceType == null)
            {
                return;
            }
            if (cboServiceType.SelectedItem != null)
            {
                //当服务类型为“标准服务”时，行金额显示为具体数值，当服务类型为“宇通服务”和“其他服务”时，行金额显示0
                DataRowView dr = (DataRowView)cboServiceType.SelectedItem;
                dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_cbx1_WORK_SERVICE_TYPE.Name].Value = dr["dic_name"];
                dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_cbx1_WORK_SERVICE_TYPE.Name].Tag = dr["dic_code"];
                if (dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_cbx1_WORK_SERVICE_TYPE.Name].Tag.ToString() == DbDic2Enum.OSN_SERVICE_TYPE_01)//标准服务
                {
                    //工时单价
                    string strfixed = string.Empty;
                    if (dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_txt1_WORK_FIXED.Name].Value!=null && !string.IsNullOrEmpty(dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_txt1_WORK_FIXED.Name].Value.ToString()))
                    {
                         strfixed = dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_txt1_WORK_FIXED.Name].Value.ToString();
                    }
                    string strtime = string.Empty;
                    if (dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_txt1_WORK_TIME.Name].Value!= null && !string.IsNullOrEmpty(dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_txt1_WORK_TIME.Name].Value.ToString()))
                    {
                        //工时
                         strtime = dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_txt1_WORK_TIME.Name].Value.ToString();
                    }
                    double doufixid, doutime,douretult = 0.00;

                    if(double.TryParse(strfixed,out doufixid) && double.TryParse(strtime,out doutime))
                    {
                        douretult = doufixid * doutime;
                    }    

                    //行金额显示为具体数值 不需要保存两位小数，不需要四舍五入
                    dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_txt1_WORK_AMOUNT.Name].ReadOnly = true;
                    dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_txt1_WORK_AMOUNT.Name].Value = douretult;

                }
                else
                {
                    //行金额显示0
                    dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_txt1_WORK_AMOUNT.Name].Value = 0;
                    dgv_tb_maintain_three_guaranty_item.CurrentRow.Cells[dgv_txt1_WORK_AMOUNT.Name].ReadOnly = true;
                }
            }
        }
        /// <summary>
        /// 结束编辑
        /// 作者：李德彦
        /// 时间：2015年12月7日
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void dgv_tb_maintain_three_guaranty_item_CellEndEdit(object sender, DataGridViewCellEventArgs e)
        {
            try
            {
                if (cboServiceType != null)
                {
                    cboServiceType.SelectedValueChanged -= new EventHandler(cboServiceType_SelectedIndexChanged);
                    cboServiceType = null;
                }
            }
            catch (Exception ex)
            {
                GlobalStaticObj.GlobalLogService.WriteLog(LocalOperation.GetStringByKey("sanbaofuwuzengjiachuangtidanyuangejieshuyichang", "三包服务增加窗体，单元格结束编辑事件异常：") + ex.Message);
            }
        }
        #endregion