How to determine if a type is a type of collection?

Question

I am trying to determine if a runtime type is some sort of collection type. What I have below works, but it seems strange that I have to name the types that I believe to be coll

Answer 1

Really all of these types inherit IEnumerable. You can check only for it:

bool IsEnumerableType(Type type)
{
    return (type.GetInterface(nameof(IEnumerable)) != null);
}

or if you really need to check for ICollection:

bool IsCollectionType(Type type)
{
    return (type.GetInterface(nameof(ICollection)) != null);
}

Look at "Syntax" part:

• List<T>

• IList

• ICollection

Answer 2

You can use linq, search for an interface name like

yourobject.GetType().GetInterfaces().Where(s => s.Name == "IEnumerable")

If this has values is a instance of IEnumerable.

Answer 3

You can use this helper method to check if a type implements an open generic interface. In your case you can use DoesTypeSupportInterface(type, typeof(Collection<>))

public static bool DoesTypeSupportInterface(Type type,Type inter)
{
    if(inter.IsAssignableFrom(type))
        return true;
    if(type.GetInterfaces().Any(i=>i. IsGenericType && i.GetGenericTypeDefinition()==inter))
        return true;
    return false;
}

Or you can simply check for the non generic IEnumerable. All collection interfaces inherit from it. But I wouldn't call any type that implements IEnumerable a collection.