using System;

public class Program

{

    public class A 

    {

        public string Value {get;set;}

    }

    public static void Main()

    {

        var item = new A

        {

            Value = "foo"

        };

        Console.WriteLine(item.Value);

        PassToFunction(item);

        Console.WriteLine(item.Value);

    }

    public static void PassToFunction(A item)

    {

        item = new A

        {

            Value = "bar"

        };

        Console.WriteLine(item.Value);

    }

}