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

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 collection types in an array like I have done.

In the code below, the reason for the generic logic is because, in my app, I expect all collections to be generic.

bool IsCollectionType(Type type)
{
    if (!type.GetGenericArguments().Any())
        return false;

    Type genericTypeDefinition = type.GetGenericTypeDefinition();
    var collectionTypes = new[] { typeof(IEnumerable<>), typeof(ICollection<>), typeof(IList<>), typeof(List<>) };
    return collectionTypes.Any(x => x.IsAssignableFrom(genericTypeDefinition));
}

How would I refactor this code to be smarter or simpler?

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

If you need to exclude strings (which are essentially an IEnumerable<char>), use the following function:

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

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.

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.

This solution will take care of ICollection and ICollection<T>.

	static bool IsCollectionType(Type type)
	{
		return type.GetInterfaces().Any(s => s.Namespace == "System.Collections.Generic" && (s.Name == "ICollection" || s.Name.StartsWith("ICollection`")));
	}