Sqlsugar更新时，设置数据库中已有数据字段为空

			//entity为数据实体想要设置时间字段为空，则调用更新方法时使用updateColumns对要修改字段进行编辑
			entity.StopStatus = "0";
            entity.Status = "3";
            entity.DownEndTime = null;
            entity.ModifyDate = DateTime.Now;
            entity.ModifyUserId = App.User.FindFirst(ClaimConst.CLAINM_USERID)?.Value;
            entity.ModifyUserName = App.User.FindFirst(ClaimConst.CLAINM_REALNAME)?.Value;
            await _repairRepository.AsUpdateable(entity).UpdateColumns(it => new { it.StopStatus,it.Status, it.DownEndTime,it.ModifyDate,it.ModifyUserId,it.ModifyUserName }).CallEntityMethod(m => m.Updator()).ExecuteCommandAsync();