本篇内容主要讲解“强制转换为值类型“System.Double”失败的原因”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“强制转换为值类型“System.Double”失败的原因”吧!

目前成都创新互联公司已为上1000家的企业提供了网站建设、域名、虚拟主机、网站托管、服务器托管、企业网站设计、松原网站维护等服务，公司将坚持客户导向、应用为本的策略，正道将秉承"和谐、参与、激情"的文化，与客户和合作伙伴齐心协力一起成长，共同发展。

  foreach (var item in entityList)
                {
                    ChannelReportDto channelReportDto = new ChannelReportDto();
                    channelReportDto.Id = item.Id;
                    channelReportDto.YueziCenterId = item.YueziCenterId;
                    channelReportDto.YueziCenterName = item.YueziCenterName;
                    channelReportDto.ChannelName = item.ChannelName;
                    channelReportDto.SumProfitAmount = OrderServiceProjectresult.Where(w => w.ChannelId == item.Id && w.IsDeleted == false).Select(s => s.SumProfitAmount).Sum(); 
                    channelReportDto.SettleProfitAmount = OrderServiceProjectresult.Where(w => w.ChannelId == item.Id && w.IsSettlement == true).Select(s => s.SumProfitAmount).Sum();
                    channelReportDto.NoSettleProfitAmount = OrderServiceProjectresult.Where(w => w.ChannelId == item.Id && w.IsSettlement == false).Select(s => s.SumProfitAmount).Sum();
                    list.Add(channelReportDto);

                }

这样写的时候 就报了这个错 The cast to value type 'System.Double' failed because the materialized value is null. Either the result type's generic parameter or the query must use a nullable type.

主要原因是没有适合查询条件的行 去计算，

所以改成以下写法就OK

 foreach (var item in entityList)
                {
                    ChannelReportDto channelReportDto = new ChannelReportDto();
                    channelReportDto.Id = item.Id;
                    channelReportDto.YueziCenterId = item.YueziCenterId;
                    channelReportDto.YueziCenterName = item.YueziCenterName;
                    channelReportDto.ChannelName = item.ChannelName;
                    channelReportDto.SumProfitAmount = OrderServiceProjectresult.Where(w => w.ChannelId == item.Id && w.IsDeleted == false).Sum(s =>(double?)s.SumProfitAmount)??0.00; 
                    channelReportDto.SettleProfitAmount = OrderServiceProjectresult.Where(w => w.ChannelId == item.Id && w.IsSettlement == true).Sum(s => (double?)s.SumProfitAmount) ?? 0.00;
                    channelReportDto.NoSettleProfitAmount = OrderServiceProjectresult.Where(w => w.ChannelId == item.Id && w.IsSettlement == false).Sum(s => (double?)s.SumProfitAmount) ?? 0.00;
                    list.Add(channelReportDto);

                }

到此，相信大家对“强制转换为值类型“System.Double”失败的原因”有了更深的了解，不妨来实际操作一番吧！这里是创新互联网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！

文章题目：强制转换为值类型“System.Double”失败的原因
地址分享：http://myzitong.com/article/pgcpdo.html