Question

I’m trying to compare two IList<T> by their Type. Both lists have the same T and therefore I thought they should have the same type.

In debug-mode in Visual Studio in the tooltip I can read the types of both and it is the same.

But Equals() ant the == Operator return both false.

Can anyone explanin this weired behavior?

Little Example:

class Program
{
    static void Main(string[] args)
    {
        IList<string> list1 = new List<string>();
        IList<string> list2 = new List<string>();

        var type1 = list1.GetType();
        var type2 = typeof(IList<string>);

        if (type1.Equals(type2))
        {
            Console.WriteLine("equal");
        }
        else
        {
            Console.WriteLine("non equal");
        }

        Console.ReadLine();
    }
}

==> non equal

Edit:
I coose a bad Example, this one shows the way I was trying to to it.

I’m using .Net 3.5

Answer 1

Yes, you’re comparing two types: List<string> and IList<string>. They’re not the same type, and I don’t know why you’d expect them to be the same.

It’s unclear what you’re trying to do, but you might want to use Type.IsAssignableFrom. For example, in your example,

Console.WriteLine(type2.IsAssignableFrom(type1));

will print True.

---

Answer from before the edit…

Unable to reproduce:

using System;
using System.Collections.Generic;

class Test
{
    static void Main()
    {
        IList<string> list1 = new List<string>();
        IList<string> list2 = new List<string>();

        var type1 = list1.GetType();
        var type2 = list2.GetType();

        Console.WriteLine(type1.Equals(type2)); // Prints True
    }
}

Is it possible that in your real code, they’re both implementations of IList<string>, but different implementations, e.g.

IList<string> list1 = new List<string>();
IList<string> list2 = new string[5];

That will show the types being different, because one is a List<string> and the other is a string[].