Simplify C# code to obtain number of elements in an enum

Question

In C# it's possible to get the number of elements in an enum using this code:

int numberOfElements = Enum.GetNames(typeof(MyEnum)).Length;

How can this code be put into it's own function, be it a normal function, a static one, extension or a generic, so that the call to it can be simplified to something like:

int numberOfElements = GetEnumEntries(MyEnum);     // something like this
int numberOfElements = GetEnumEntries<MyEnum>();   // or this

For instance if I try this:

static public int GetEnumEntries(System.Type t) {
    int numberOfElements = System.Enum.GetNames(typeof(t)).Length;
}

I get the error 'the type or namespace t could not be found'

Just to correct your trial code: You should remove typeof(t), t is already a type, directly use t there. In the caller code than you would need to check as GetNumEntries( typeof( MyEnum )) - assuming you completed the method with a return). — Cetin Basoz, Sep 19 '16 at 10:50

Bill Tür stands with Ukraine · Accepted Answer · 2016-09-19T10:58:24.657

3

You can use the generic approach. The hardest part is to limit the type parameter to an enum which can't be solely done at compile time. But with the method mentioned in this answer you can use this:

public static int GetEnumEntries<T>() where T : struct, IConvertible
{
    if (!typeof(T).IsEnum)
        throw new ArgumentException("T must be an enumerated type");

    return Enum.GetNames(typeof(T)).Length;
}

edited Sep 19 '16 at 10:58

answered Sep 19 '16 at 10:51

Bill Tür stands with Ukraine

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Great answer, though I don't follow why it's private? – Matt Parkins Sep 19 '16 at 10:57
@MattParkins I think it's because of the the IntelliSense. It defaults method generation with private access modifier see [image](http://i.stack.imgur.com/nHp5g.png) – Orkhan Alikhanov Sep 19 '16 at 11:04

score 2 · Answer 2 · answered Sep 19 '16 at 10:45

2

private static int GetEnumEntries<T>()
{
    return Enum.GetNames(typeof(T)).Length;
}

answered Sep 19 '16 at 10:45

Orkhan Alikhanov

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Cannot believe it was that easy. I thought I'd tried this route. – Matt Parkins Sep 19 '16 at 10:46

score 0 · Answer 3 · answered Sep 19 '16 at 10:50

0

typeof(t) will allways evaluate to System.Type instead of the type of actual type of your enumeration. Thus use t directly

System.Enum.GetNames(t).Length

answered Sep 19 '16 at 10:50

MakePeaceGreatAgain

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then he has to call it `GetEnumEntries(typeof(MyEnum))`. It changes nothing – Orkhan Alikhanov Sep 19 '16 at 10:51
@OrkhanAlikhanov Sure, but he has to provide the type anyway. The method makes it only some characters shorter. In your solution the same also applies, only the `typeof` is left. – MakePeaceGreatAgain Sep 19 '16 at 10:55
1

typeof(t) wouldn't even compile, t is a variable. – Cetin Basoz Sep 21 '16 at 08:18

Simplify C# code to obtain number of elements in an enum

3 Answers3