强制转换为值类型“十进制"失败，因为实例化值为null [英] The cast to value type 'Decimal' failed because the materialized value is null

问题描述

此查询存在问题，它引发了错误.

I am having a problem with this query it's throwing an error.

var TotalToDatePayable = (  from ori in db.GetAll<WMPORI>()
                           where ori.CTMSysID == ctmSysId
                          select ori.ExB4Taxes).Sum();

我尝试了以下代码，原因是

I tried below code from another similar question but that did not solve my problem:

 var TotalToDatePayable = (Decimal?)(  from ori in db.GetAll<WMPORI>()
                                      where ori.CTMSysID == ctmSysId
                                     select ori.ExB4Taxes).Sum()) ?? 0;

推荐答案

您需要在查询内部将ori.ExB4Taxes强制转换为decimal?.

You need to cast ori.ExB4Taxes to decimal? inside the query.

var TotalToDatePayable = (from ori in db.GetAll<WMPORI>()
                          where ori.CTMSysID == ctmSysId
                          select (Decimal?) ori.ExB4Taxes).Sum() ?? 0;

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