How to do Linq aggregates when there might be an empty set?
- by Shaul
I have a Linq collection of Things, where Thing has an Amount (decimal) property.
I'm trying to do an aggregate on this for a certain subset of Things:
var total = myThings.Sum(t => t.Amount);
and that works nicely. But then I added a condition that left me with no Things in the result:
var total = myThings.Where(t => t.OtherProperty == 123).Sum(t => t.Amount);
And instead of getting total = 0 or null, I get an error:
System.InvalidOperationException: The null value cannot be assigned to a member
with type System.Decimal which is a non-nullable value type.
That is really nasty, because I didn't expect that behavior. I would have expected total to be zero, maybe null - but certainly not to throw an exception!
What am I doing wrong? What's the workaround/fix?
