如果总和值都为null，如何使linq Sum返回null [英] How to make a linq Sum return null if the summed values are all null

问题描述

我有一个看起来像这样的LINQ查询...

I have a LINQ query that looks like this...

var duration = Level3Data.AsQueryable().Sum(d => d.DurationMonths);

如果所有 d.DurationMonths 值为空，则Sum返回 0 .如果所有 d.DurationMonths 全部为 null ，如何使Sum返回 null ?还是我需要先执行一个单独的查询来消除这种情况，然后再执行总和?

If all the d.DurationMonths values are null the Sum returns 0. How can I make the Sum return null if all the d.DurationMonths are null? Or do I need to run a separate query first to eliminate this situation before performing the sum?

推荐答案

与先前关于扩展方法的建议一起-您可以使用三元运算符...

Along with the previous suggestion for an extension method - you could use a ternary operator...

var duration = Level3Data.AsQueryable().Any(d => d.DurationMonths.HasValue) 
               ? Level3Data.AsQueryable().Sum(d => d.DurationMonths) 
               : null;

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