using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var testList = new List<Test>{

                new Test {Field1 = "1", Field2 = 1},

                new Test {Field1 = "2", Field2 = 2}

            };

​

            var r = testList.FirstOrDefault();

            r.Field2 = 2222;

        Console.WriteLine(testList[0].Field2);

    }

}

public class Test {

        public string Field1 { get; set; }

        public int Field2 { get; set; }

    }