AverageAsync throws exception when enumeration is empty

Question

Using Entity Framework Core I have the following query:

var avgDuration = await projects.AverageAsync(x => x.Duration);

When the enumeration projects is empty I get the following error:

InvalidOperationException: Sequence contains no elements. 

Is there a way to AverageAsync to not throw exception when enumeration as not elements.

Should not just return null?

Answer 1

Is there a way to AverageAsync to not throw exception when enumeration as not elements.

Should not just return null?

Average and AverageAsync (as well as Min, Max) will return null on empty set when the value type is nullable. If it is not, just promote it to the corresponding nullable type using C# cast operator.

For instance, if in your sample the type of x.Duration is int, then use int? cast:

var avgDuration = await projects.AverageAsync(x => (int?)x.Duration);

And if you want to get 0 (zero) when the source set is empty, then simply apply ?? 0 to the result.