How to get the type of T from a member of a generic class or method

Question

Let's say I have a generic member in a class or method, like so:

public class Foo<T> {     public List<T> Bar { get; set; }          public void Baz()     {         // get type of T     }    } 

When I instantiate the class, the T becomes MyTypeObject1, so the class has a generic list property: List<MyTypeObject1>. The same applies to a generic method in a non-generic class:

public class Foo {     public void Bar<T>()     {         var baz = new List<T>();                  // get type of T     } } 

I would like to know what type of objects the list of my class contains. So what type of T does the list property called Bar or the local variable baz contain?

I cannot do Bar[0].GetType(), because the list might contain zero elements. How can I do it?

Answer 1

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 2

(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; 

Using new TypeInfo:

using System.Reflection; // ... var type = abc.GetType().GetTypeInfo().GenericTypeArguments[0];