gistfile1.cs

using System;
using System.Collections.Generic;

struct S
{
    ValueType x;

    static void Main()
    {
        var s = new S();
        ValueType v = s;
        dynamic d = v;
        d.x = v;
        s = (S) v;

        var set = new HashSet<S> { s };

        Console.WriteLine(set.Contains(s)); // Can you tell the result?
    }
}