C#•16mo ago

How to perform LINQ Average against collection of TValue constrained as INumber<TValue>

I would like to perform an average against a collection of TValue wherein I know TValue is a number because I've constrained it to INumber<TValue>. However, when trying to use it in the LINQ expression, it doesn't appear to know how to handle the arbitrary number type:

var avg = group.Average(v => v.Value);

var avg = group.Average(v => v.Value);

CS0029: Cannot implicitly convert type 'TValue' to 'long?'

Any guesses as to how I can handle this generically without writing a separate overload for every numeric type? Thank you!

12 Replies

WhitOP•16mo ago

Oddly, if I simply cast v.Value as dynamic, VS seems to think I'm casting to an int and returns a double and that's not right - as it might be a decimal that was provided.

Denis•16mo ago

Avoid using dynamic

WhitOP•16mo ago

I'd like to, but I'm not seeing much in the way of alternatives It's the only way not giving me squigglies

Denis•16mo ago

And if you avoid linq altogether and write a classic loop? Average should give you an double anyway

WhitOP•16mo ago

That might be blasphemy.. but also might be what's called for

Denis•16mo ago

So if you want it to be the same type as the input, you have to cast Not at all, I'd say it is perfectly fine. There are different types of averages anyway, so this allows you to be more specific

WhitOP•16mo ago

I'll give that a whirl - thanks for the suggestion

Denis•16mo ago

If group is an Ienumerable, make sure to materialize it to an array or smth. Or change the input argument to an iReadonlycollection This is to avoid multiple enumerations

Moods•16mo ago

Just curious, did you implement the Average method yourself? If so may I see it?

WhitOP•16mo ago

Working on it You're right - makes sense to return the average as a double

    public static double Average<TValue>(this IEnumerable<TValue> values)
        where TValue : INumber<TValue>
    {
        double sum = 0;
        var count = 0;

        foreach (var value in values.ToList())
        {
            sum += Convert.ToDouble(value);
            count++;
        }

        return sum / count;
    }

    public static double Average<TValue>(this IEnumerable<TValue> values)
        where TValue : INumber<TValue>
    {
        double sum = 0;
        var count = 0;

        foreach (var value in values.ToList())
        {
            sum += Convert.ToDouble(value);
            count++;
        }

        return sum / count;
    }

@moooodie

Moods•16mo ago

Oh you removed the function parameter

Denis•16mo ago

No need to do ToList since you are accessing the list only once Sorry, I didn't think of counting the number of entries in the loop

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How to perform LINQ Average against collection of TValue constrained as INumber<TValue>