CODEWITHSUNDEEP
c#reflectionienumerable
Sarov
Sarov

Reputation: 645

How to tell if something is an IEnumerable<>?

I've got a Type.

How can I tell if it's an IEnumerable<>?

These:

typeof(IEnumerable<>).IsAssignableFrom(memberType);
typeof(IEnumerable<object>).IsAssignableFrom(memberType);

return false for IEnumerable<int>

Whereas this:

typeof(IEnumerable).IsAssignableFrom(memberType);

returns true for string.

Upvotes: 3

Views: 951

Answers (2)

Sarov
Sarov

Reputation: 645

Well... I found a way to do it...

private static bool IsGenericEnumerable(this [NotNull] Type type) =>
            typeof(IEnumerable<>).IsAssignableFrom(type)
            || typeof(IEnumerable<object>).IsAssignableFrom(type)
            || (typeof(IEnumerable<char>).IsAssignableFrom(type) && type != typeof(string))
            || typeof(IEnumerable<byte>).IsAssignableFrom(type)
            || typeof(IEnumerable<sbyte>).IsAssignableFrom(type)
            || typeof(IEnumerable<ushort>).IsAssignableFrom(type)
            || typeof(IEnumerable<short>).IsAssignableFrom(type)
            || typeof(IEnumerable<uint>).IsAssignableFrom(type)
            || typeof(IEnumerable<int>).IsAssignableFrom(type)
            || typeof(IEnumerable<ulong>).IsAssignableFrom(type)
            || typeof(IEnumerable<long>).IsAssignableFrom(type)
            || typeof(IEnumerable<float>).IsAssignableFrom(type)
            || typeof(IEnumerable<double>).IsAssignableFrom(type)
            || typeof(IEnumerable<decimal>).IsAssignableFrom(type)
            || typeof(IEnumerable<DateTime>).IsAssignableFrom(type);

...but that's kind of horrible and I hope there's a better way.

Upvotes: 1

Marc Gravell
Marc Gravell

Reputation: 1062492

Reflection is fun; side note: keep in mind that you can implement IEnumerable<X> and IEnumerable<Y> (etc) on the same type, so for simplicity here I'm just reporting the first found arbitrarily:

static void Main()
{
    Console.WriteLine(FindFirstIEnumerable(typeof(int))); // null
    Console.WriteLine(FindFirstIEnumerable(typeof(string))); // System.Char
    Console.WriteLine(FindFirstIEnumerable(typeof(Guid[]))); // System.Guid
    Console.WriteLine(FindFirstIEnumerable(typeof(IEnumerable<float>))); // System.Single
}

static Type FindFirstIEnumerable(Type type)
{
    if (type == null || !typeof(IEnumerable).IsAssignableFrom(type))
        return null; // anything IEnumerable<T> *must* be IEnumerable
    if (type.IsInterface && type.IsGenericType
        && type.GetGenericTypeDefinition() == typeof(IEnumerable<>))
    {
        return type.GetGenericArguments()[0];
    }
    foreach(var iType in type.GetInterfaces())
    {
        if (iType.IsGenericType &&
            iType.GetGenericTypeDefinition() == typeof(IEnumerable<>))
        {
            return iType.GetGenericArguments()[0];
        }
    }
    return null;
}

Upvotes: 4

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