Question

How would you go about using LINQ aggregate functions (ex. Sum, Average) on collections of bytes, shorts, and unsigned values? Granted, I’m a new C# programmer, but I can’t even figure out how to get something that compiles let alone has proper output.

Here’s a trivial example of what I am trying to do:

short[] numbersArray = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
short sumArray = numbersArray.Sum();

or

List<short> numbersList = new List<short> { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
short sumList = numbersList.Sum();

I can’t either of these samples to work. If I change the data type to int it works, but I can’t get it to work for shorts, bytes, uints, etc.

What am I doing wrong?

Answer 1

Enumerable.Sum<T>() is only defined for IEnumerable<T> where T in

double,
double?
int,
int?
decimal,
decimal?
long,
long?
float,
float?

This is because there is no addition operator^* for short or any of the other primitive types (short + short is int, for example).

You have to say:

short[] numbersArray = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int sumArray = numbersArray.Sum(x => (int)x);

and less explicitly you can get away with

short[] numbersArray = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int sumArray = numbersArray.Sum(x => x);

In this case, you are now invoking the overload:

int Enumerable.Sum<short>(
    this IEnumerable<short> source,
    Func<short, int> selector
)

^*: Here I mean “operator” in the sense of an function F:(short x short) -> short.