How to prevent duplicate values in enum?

Question

Hi,

I wonder is there a way to prevent an enum with duplicate keys to compile?

For instance this enum below will compile

public enum EDuplicates
{
    Unique,
    Duplicate = 0,
    Keys = 1,
    Compilation = 1
}

Although this code

Console.WriteLine(EDuplicates.Unique);
Console.WriteLine(EDuplicates.Duplicate);
Console.WriteLine(EDuplicates.Keys);
Console.WriteLine(EDuplicates.Compilation);

Will print

Duplicate
Duplicate
Keys
Keys

Answer 1

This isn't prohibited by the language specification, so any conformant C# compiler should allow it. You could always adapt the Mono compiler to forbid it - but frankly it would be simpler to write a unit test to scan your assemblies for enums and enforce it that way.

Answer 2

public bool ValidateAllDistinct(Type enumType)
{
    return !Enum.GetNames(enumType).All(outerName
        => Enum.GetNames(enumType).Any(innerName
            => innerName == outerName 
                ? true 
                : Enum.Parse(enumType, innerName) != Enum.Parse(enumType, outerName)));
}

I simple test method for your unittest.