using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        ICriterion ci = new Criterion("a");

        Criterion c = new Criterion("a");

        Console.WriteLine(IsBoxed(ci));

        Console.WriteLine(IsBoxed(c));

    }

​

    public static bool IsBoxed<T>(T value)

    {

        return 

            (typeof(T).IsInterface || typeof(T) == typeof(object)) &&

            value != null &&

            value.GetType().IsValueType;

    }

}

​

public interface ICriterion {}

​

public struct Criterion : ICriterion {

    public Criterion(string criteria) {

        Criteria = criteria;

    }

    public string Criteria {get;set;}

}

​