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David Klempfner
David Klempfner

Reputation: 9890

Get max value from enum using generics

How can I get the max int value from an enum using generics?

I have tried the following however it displays the following compilation error:

Cannot implicitly convert T to int

    int maxValue = GetMaxValue<SomeEnum>(typeof(SomeEnum)); //expecting 2

    private static int GetMaxValue<T>(Type enumType)
    {
        return Enum.GetValues(enumType).Cast<T>().Max();
    }

    public enum SomeEnum
    {
        ValueOne = 1,
        Value = 2
    }

Upvotes: 3

Views: 468

Answers (3)

Dmitrii Bychenko
Dmitrii Bychenko

Reputation: 186803

In case of C# 7.3 or later version, you can implement Sweeper's idea in a bit different way (with a help of where T : Enum constraint):

public static T GetMaxValue<T>() where T : Enum {
  return Enum.GetValues(typeof(T)).Cast<T>().Max();
}

...

SomeEnum max = GetMaxValue<SomeEnum>();

Please, note, that the result is enum itself and that's why we don't have any problems with enum underlying type (byte, short int, long)

Upvotes: 3

Sweeper
Sweeper

Reputation: 272555

You need to cast to int, not T. And you don't actually need the Type parameter (unless you don't know the type at compile time), since you can just do typeof(T):

private static int GetMaxValue<T>()
{
    return Enum.GetValues(typeof(T)).Cast<int>().Max();
}

// usage:
GetMaxValue<SomeEnum>() // 2

If your enums have long or some other type as the underlying type, you can specify another type parameter to cast them to:

private static U GetMaxValue<T, U>() where U : struct
{
    return Enum.GetValues(typeof(T)).Cast<U>().Max();
}

// usage:
GetMaxValue<SomeLongEnum, long>()

Upvotes: 2

shingo
shingo

Reputation: 27156

Use Convert.ToInt32

 return Convert.ToInt32(Enum.GetValues(enumType).Cast<T>().Max());

But usually I do this, more faster than calling GetValues

public enum SomeEnum
{
    ValueOne = 1,
    Value = 2,
    END
}

return (int)(SomeEnum.END - 1);

Upvotes: 0

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