Possible to pass null from Powershell to a .Net API that expects a string?

Question

API:

namespace ClassLibrary1
{
    public class Class1
    {
        public static string Test(string input)
        {
            if (input == null)
                return "It's null";
            if (input == string.Empty)
                return "It's empty";
            else
                return "Non-empty string of length " + input.Length;
        }
    }
}

Script:

add-type -path C:\temp\ClassLibrary1\ClassLibrary1\bin\Debug\ClassLibrary1.dll
[classlibrary1.class1]::Test($null)
[classlibrary1.class1]::Test([object]$null)
[classlibrary1.class1]::Test([psobject]$null)
[classlibrary1.class1]::Test($dummyVar)
[classlibrary1.class1]::Test($profile.dummyProperty)

Output:

It's empty
It's empty
It's empty
It's empty
It's empty

What am I missing?

Answer 1

In order to pass a null value to an API call, use [NullString]::Value.

Answer 2

According to this MS connect issue, this is a known problem. There are a couple workarounds posted there, too, like using reflection to pass the paramaters (which is clever, but kinda silly that it's required). Cheers!