C# 如何获取linq中具有最大日期的数据

这是一个linq查询，表“Timesheet_Log”有一个日期时间类型为DateTime的DT_CR列，我想得到最新DT_CR日期的查询，怎么可能呢

  var getEmployeeNames = (from emps in reslandentity.EMPLOYEE
                                join timesheet in reslandentity.TIMESHEET on emps.ID equals timesheet.RES_ID
                                join weekcal in reslandentity.WEEK_CALENDER on timesheet.WEEK_CAL_ID equals weekcal.ID
                                join log in reslandentity.TIMESHEET_LOG on timesheet.ID equals log.TIMESHEET_ID
                                join workflow in reslandentity.TIMESHEET_WORKFLOW on log.WORKFLOW_ID equals workflow.ID                                    
                                where weekcal.WEEK_START_DT.Month == month                                    
                                orderby log.DT_CR select new TimesheetModel
                                {
                                    EMP_ID = emps.ID,
                                    EMPLOYEE_NAME = emps.FIRST_NAME + " " + emps.LAST_NAME,
                                    RES_TYPE = workflow.ORG_RES_TYPE,
                                    EMP_STATUS = workflow.ACTION,
                                    SDate = weekcal.WEEK_START_DT,
                                    EDate = weekcal.WEEK_END_DT,
                                    DT_CR=log.DT_CR
                                }).Distinct().ToList();
   model.GetTimeSheetDetails = getEmployeeNames;

请帮我查询一下

 var getEmployeeNames = (from emps in reslandentity.EMPLOYEE
                            join timesheet in reslandentity.TIMESHEET on emps.ID equals timesheet.RES_ID
                            join weekcal in reslandentity.WEEK_CALENDER on timesheet.WEEK_CAL_ID equals weekcal.ID
                            join log in reslandentity.TIMESHEET_LOG on timesheet.ID equals log.TIMESHEET_ID
                            join workflow in reslandentity.TIMESHEET_WORKFLOW on log.WORKFLOW_ID equals workflow.ID                                    
                            where weekcal.WEEK_START_DT.Month == month                                    
                            //orderby log.DT_CR 
                            select new TimesheetModel
                            {
                                EMP_ID = emps.ID,
                                EMPLOYEE_NAME = emps.FIRST_NAME + " " + emps.LAST_NAME,
                                RES_TYPE = workflow.ORG_RES_TYPE,
                                EMP_STATUS = workflow.ACTION,
                                SDate = weekcal.WEEK_START_DT,
                                EDate = weekcal.WEEK_END_DT,
                                DT_CR=log.DT_CR
                            }).OrderByDescending(x=>x.DT_CR).FirstorDefault();

或

---

您还没有明确表示您只期望一个结果还是一个结果列表（每个时间表1个）

如果您只需要一个结果，lti Tyangi的答案就可以了

如果需要每个时间表的结果，可以尝试以下操作：

var getEmployeeNames = (from emps in reslandentity.EMPLOYEE
                            join timesheet in reslandentity.TIMESHEET on emps.ID equals timesheet.RES_ID
                            join weekcal in reslandentity.WEEK_CALENDER on timesheet.WEEK_CAL_ID equals weekcal.ID
                            join mxLog in (
                                from lg in reslandentity.TIMESHEET_LOG
                                group lg by lg.TIMESHEET_ID into lgGrp
                                select new {lgGrp.Key, DT_CR = lgGrp.Max(x => x.DT_CR)}
                            ) on timesheet.ID equals mxLog.Key
                            join log in reslandentity.TIMESHEET_LOG on new { a = mxLog.Key, b = mxLog.DT_CR} equals new{ a = log.TIMESHEET_ID, b = log.DT_CR}
                            join workflow in reslandentity.TIMESHEET_WORKFLOW on log.WORKFLOW_ID equals workflow.ID                                    
                            where weekcal.WEEK_START_DT.Month == month                                    
                            orderby log.DT_CR select new TimesheetModel
                            {
                                EMP_ID = emps.ID,
                                EMPLOYEE_NAME = emps.FIRST_NAME + " " + emps.LAST_NAME,
                                RES_TYPE = workflow.ORG_RES_TYPE,
                                EMP_STATUS = workflow.ACTION,
                                SDate = weekcal.WEEK_START_DT,
                                EDate = weekcal.WEEK_END_DT,
                                DT_CR=log.DT_CR
                            }).Distinct().ToList();
   model.GetTimeSheetDetails = getEmployeeNames;

---

在这里，我们加入到每个时间表的日志分组中，以获得每个时间表的最大日期，然后根据时间表的id和该日期加入到日志中

您想要具有最新日期的单个模型吗？如果您想要模型列表，那么请指定您想要选择它们的条件。我应该以Max（DT_CR）的形式获取数据，但我研究了如何写入。对不起，我不明白您想要获取什么。查询中没有分组-要从哪些数据中选择最大日期？使用ToList（），是否需要从所有记录中以单个记录的形式获取最大日期？然后在where条件中获取最大范围后使用FirstOrDefault（），或者使用max，例如var q=（从context.Tablename where…）中的n开始）。选择（x=>x.nameofcolumn.max（）；你有一个订单。然后，您可以使用

.Take（1）

（不确定如何用非方法语法编写）从有序列表中获取第一项。您可能希望按降序获取最大日期。获取错误，如“LINQ to Entities中不支持指定的类型成员'DT_CR'。只支持初始值设定项、实体成员和实体导航属性。”您的答案中有一个输入错误。在这两种情况下，您都意外地将select以及原始订单注释掉了。谢谢Chris，@sanjay:我希望您一定没有复制相同的内容（注释了select）。谢谢@James S，linq有复杂的行为，它以不同的方式进行分组

var getEmployeeNames = (from emps in reslandentity.EMPLOYEE
                            join timesheet in reslandentity.TIMESHEET on emps.ID equals timesheet.RES_ID
                            join weekcal in reslandentity.WEEK_CALENDER on timesheet.WEEK_CAL_ID equals weekcal.ID
                            join mxLog in (
                                from lg in reslandentity.TIMESHEET_LOG
                                group lg by lg.TIMESHEET_ID into lgGrp
                                select new {lgGrp.Key, DT_CR = lgGrp.Max(x => x.DT_CR)}
                            ) on timesheet.ID equals mxLog.Key
                            join log in reslandentity.TIMESHEET_LOG on new { a = mxLog.Key, b = mxLog.DT_CR} equals new{ a = log.TIMESHEET_ID, b = log.DT_CR}
                            join workflow in reslandentity.TIMESHEET_WORKFLOW on log.WORKFLOW_ID equals workflow.ID                                    
                            where weekcal.WEEK_START_DT.Month == month                                    
                            orderby log.DT_CR select new TimesheetModel
                            {
                                EMP_ID = emps.ID,
                                EMPLOYEE_NAME = emps.FIRST_NAME + " " + emps.LAST_NAME,
                                RES_TYPE = workflow.ORG_RES_TYPE,
                                EMP_STATUS = workflow.ACTION,
                                SDate = weekcal.WEEK_START_DT,
                                EDate = weekcal.WEEK_END_DT,
                                DT_CR=log.DT_CR
                            }).Distinct().ToList();
   model.GetTimeSheetDetails = getEmployeeNames;