using System;

using System.Collections.Generic;

public class Program

{

    struct A

    {

        public string S;

        public A() { S = "Hello"; }

    }

    public static void Main()

    {

        var list = new List<A>() { new A() };

        var item = list[0];

        item.S = "World";

​

        Console.WriteLine(item.S);

        Console.WriteLine(list[0].S);

    }

}