Restricting generic function to only work on Enums [duplicate]

This question already has answers here: Anyone know a good workaround for the lack of an enum generic constraint? (12 answers) Interesting "params of ref" feature, any workarounds? (5 answers) Closed 9 years ago.

I have the following generic function:

public SomeType SomeFunction<T>(T value)
{
}

I would now like to restrict this generic function to work only with Enums so I tried the following开发者_开发百科:

public SomeType SomeFunction<T>(T value) where T : System.Enum
{
}

But this resulted in:

error CS0702: Constraint cannot be special class 'System.Enum'

Is there a work around and out of curiosity does anyone know the reason why this type of constraint isn't allowed?

---

You can't. You can restrict it to value types, but that's all. Restricting it to enums can only be done using runtime checking:

public SomeType SomeFunction<T>(T value) where T : struct
{
    if (!typeof(T).IsEnum)
    {
        throw new NotSupportedException("Only enums are supported.");
    }
}

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Steven is correct, but you can narrow it a little before you throw an exception

public SomeType SomeFunction<T>(T value) where T : struct