Question

What is the correct code to cast an object back to a generic list like so?

Type x = typeof(MyClass);
object o = new List<MyClass>();

List<x> l = o as List<x>; // Not working

EDIT:
Maybe it wasn’t all clear: The object is a list of a generic type which i don’t know at compile time.. nevertheless List has functions like “Add” i can call anyway, like:

l.Add((new MyClass() as object)) as x);

Answer 1

List<MyClass> l = (List<MyClass>)o;

or

List<MyClass> l = o as List<MyClass>;

---

Do you mean

List<> l = o as List<>;

This is not possible until you use a generic class:

class C<T>
{
    public List<T> List = new List<T>();
}

Usage:

C<MyClass> c = new C<MyClass>();
c.List.Add(new MyClass());

---

Finally I got OP’s goal:

Type listType = typeof(List<>);
Type targetType = listType.MakeGenericType(typeof(YourClass));
List<YourClass> list = (List<YourClass>)Activator.CreateInstance(targetType);

See MSDN for details.