How to use reflection to check if a parameter is prefixed with keyword "this"? [duplicate]

This question already has an answer here:

• Using reflection to check if a method is “Extension Method” 5 answers

public static class TEST_THIS
{
    public class TEST
    {
    }
    public static void Foo(this TEST t) { }
}

How to know parameter t was prefixed with "this" via ParameterInfo of t?