Get actual type of T in a generic List

Question

How do I get the actual type of T in a generic List at run time using reflection?

Answer 1

It depends on what exactly you’re asking:

• While writing code inside a generic type Blah, how do I get the reflection type T?

  Answer: typeof(T)

• I have an object which contains a List for some type T. How do I retrieve the type T via reflection?

  Short answer: myList.GetType().GetGenericArguments()[0]

  Long answer:

  var objectType = myList.GetType();
  if (!objectType.IsGenericType() ||
      objectType.GetGenericTypeDefinition() != typeof(List<>))
  {
      throw new InvalidOperationException(
          "Object is not of type List for any T");
  }
  var elementType = objectType.GetGenericArguments()[0];