Why does LINQPad dump enum integer values as strings?

Question

I was using LinqPad to test out some Enum functions and I didn't get integers like I expected when I used .Dump(). Why did the ToList() solve the problem?

void Main()
{
    Enum.GetValues(typeof(Options)).Cast<int>().Dump();
    Enum.GetValues(typeof(Options)).Cast<int>().ToList().Dump();
}

public enum  Options 
{
   Equal,
   LessThan,
   GreaterThan
}

enter image description here

i think this is a limitation of the .Cast operation. Enum.GetValues(typeof(Options)).Cast<int>().Select(f => (int)f).Dump(); works for me. — Daniel A. White
– Daniel A. White, Commented Apr 24, 2014 at 18:44

Thomas Levesque · Accepted Answer · 2014-04-24 18:52:21Z

15

Actually, LINQPad is not the culprit here. This is because of an optimization in Enumerable.Cast:

    public static IEnumerable<TResult> Cast<TResult>(this IEnumerable source) {
        IEnumerable<TResult> typedSource = source as IEnumerable<TResult>;
        if (typedSource != null) return typedSource;
        if (source == null) throw Error.ArgumentNull("source");
        return CastIterator<TResult>(source);
    }

As you can see, if source implements IEnumerable<TResult>, then Cast just returns the source unchanged. In this case, source is of type Option[], which happens to implement IEnumerable<int>, so Cast returns an array of Option, and LINQPad dumps it.

I must admit that it came as a surprise that Option[] can be cast to IEnumerable<int>, but it seems to be the case...

edited Apr 24, 2014 at 18:52

answered Apr 24, 2014 at 18:44

Thomas Levesque

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3 Comments

Jon Skeet Over a year ago

It can't just be cast to IEnumerable<int> - it can be cast to int[]! This is a conversion that the CLR allows, but the C# language doesn't... so to make the cast compile, you have to confuse the C# compiler by converting to object first... but then it works fine.

Thomas Levesque Over a year ago

@JonSkeet, I assume that it works only because the underlying type of that enum is int?

Jon Skeet Over a year ago

Yup. Although you could cast to uint[] as well. The CLR is quite forgiving when it comes to conversions like that.

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