Handle null in LINQ sum expression

Question

I am using a LINQ query to find sum of a column and there is a slight chance that the value might be null in few cases The query I am using now is ``` int score = dbContext.domainmaps.Where(p => p.SchoolId == schoolid).Sum(v => v.domainstatement.Score ?? 0); ``` where `domainstatement` can be null and score also can be null Now after executing this query, I am getting the error The cast to value type 'Int32' failed because the materialized value is null. Either the result type's generic parameter or the query must use a nullable type. So how can I handle null exceptions effectively and return sum as an INT value?

Accepted Answer

Here

```
Sum(v => v.domainstatement.Score ?? 0);
```

you've just put the null-coalescing operator on the wrong place. Usually such error is solved by promoting the non nullable type to nullable (no `DefaultOrEmpty` and null checks are needed), but here you already have a nullable type, and with null-coalescing operator you did the opposite of what the error message is telling you - the query must use a nullable type.

Simply move it after the `Sum` call and the issue is gone:

```
Sum(v => v.domainstatement.Score) ?? 0;
```

Handle null in LINQ sum expression

Solution

Problem