强制转换为值类型“十进制"失败，因为实例化值为null

本文介绍了强制转换为值类型“十进制"失败，因为实例化值为null的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 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，原因是另一个类似的问题，但这不能解决我的问题:

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;