C# generic list <T> how to get the type of T?

Question

Hello,

Let say I have a List< T > abc = new List< T >; inside a class public class MyClass<T>//.... Later, when I initialize the class the T because MyTypeObject1. So I have a generic list of List< MyTypeObject1 >.

I would like to know, what type of object the list of my class contain. Example, the list called abc contain what type of object? I cannot do abc[0].GetType(); because the list might contain 0 element. How can I do it?

Answer 1

(note: I'm assuming that all you know is object or IList or similar, and that the list could be any type at runtime)

If you know it is a List<T>, then:

Type type = abc.GetType().GetGenericArguments()[0];

Another option is to look at the indexer:

Type type = abc.GetType().GetProperty("Item").PropertyType;

Answer 2

Try

list.GetType().GetGenericArguments()

Answer 3

If I understand correctly, your list has the same type parameter as the container class itself. If this is the case, then:

Type typeParameterType = typeof(T);

If you are in the lucky situation of having object as a type parameter, see Marc's answer.

Answer 4

May I make a question? Why do you want to know the type of T? Teoretically, generics are made just to remove the need to know the element detail implementation...

Answer 5

typeof(T) should do what you need.

Answer 6

Type:

type = list.AsEnumerable().SingleOrDefault().GetType();

Answer 7

Consider this: I use it to export 20 typed list by same way:

    private void Generate<T>()
    {
        T item = (T)Activator.CreateInstance(typeof(T));

        ((T)item as DemomigrItemList).Initialize();

        Type type = ((T)item as DemomigrItemList).AsEnumerable().FirstOrDefault().GetType();
        if (type == null) return;
        if (type != typeof(account)) //account is listitem in List<account>
        {
            ((T)item as DemomigrItemList).CreateCSV(type);
        }
    }

Answer 8

Hello, The GetGenericArgument() method has to be set on the Base Type of your instance (whose class is a generic class myClass)

otherwise, it returns a type[0]

ex: Myclass instance = new Myclass(); Type[] listTypes = typeof(instance).BaseType.GetGenericArguments();