请帮助左加入Linq [英] Please help in Left Join Linq

问题描述

它给我一个错误，因为对象没有设置为对象的实例

It giving me Error as Object is not set to instance of object

var query = (from attendace in ListAttendace_Details
                       join makeup in  ListMakeup
                       on attendace.Attendace_ID equals makeup.Attendace_ID
                       into yG
                       from y1 in yG.DefaultIfEmpty()

                       select new { Makup=y1.Attendace_ID==null?0:1,attendace.Status, attendace.ISAttend, attendace.Attendace_ID }).ToList();

推荐答案

我相信你在选择行上有例外。这些其他映射表中可能没有映射记录。哪个将返回null并且null不能被指定为选择结果，这将导致抛出您正在拥有的异常。所以尝试对你在Makup上做的其他选择字段进行空检查。



祝你好运，

OI

I believe you are having your exception on the select line. It is possible that, there is no mapping record present in these other mapping table. Which will return null and null cannot be assigned as select result and this will result in throwing the exception you are having. So try doing the null check to the other select fields you did on the Makup.

Good luck,
OI

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