C# int to enum conversion [duplicate]

Solution 1:

It's fine just to cast your int to Foo:

int i = 1;
Foo f = (Foo)i;

If you try to cast a value that's not defined it will still work. The only harm that may come from this is in how you use the value later on.

If you really want to make sure your value is defined in the enum, you can use Enum.IsDefined:

int i = 1;
if (Enum.IsDefined(typeof(Foo), i))
{
    Foo f = (Foo)i;
}
else
{
   // Throw exception, etc.
}

However, using IsDefined costs more than just casting. Which you use depends on your implemenation. You might consider restricting user input, or handling a default case when you use the enum.

Also note that you don't have to specify that your enum inherits from int; this is the default behavior.

Solution 2:

I'm pretty sure you can do explicit casting here.

foo f = (foo)value;

So long as you say the enum inherits(?) from int, which you have.

enum foo : int

EDIT Yes it turns out that by default, an enums underlying type is int. You can however use any integral type except char.

You can also cast from a value that's not in the enum, producing an invalid enum. I suspect this works by just changing the type of the reference and not actually changing the value in memory.

enum (C# Reference)
Enumeration Types (C# Programming Guide)

Solution 3:

Casting should be enough. If you're using C# 3.0 you can make a handy extension method to parse enum values:

public static TEnum ToEnum<TInput, TEnum>(this TInput value)
{
    Type type = typeof(TEnum);

    if (value == default(TInput))
    {
        throw new ArgumentException("Value is null or empty.", "value");
    }

    if (!type.IsEnum)
    {
        throw new ArgumentException("Enum expected.", "TEnum");
    }

    return (TEnum)Enum.Parse(type, value.ToString(), true);
}