using System;

using System.Collections;           

using System.Collections.Generic;

​

public class Program

{

    class DataLibrary {

        private readonly List<string> sourceList = new List<string>() { "Test1", "Test2", "Test3" };

        public IEnumerable<string> Source { get { return sourceList; } }    

    }

    class DataUser {

        private static List<string> compoundList;

        private const string DefaultFirstValue = "Test0";

        public DataUser(DataLibrary library) {

            compoundList = new List<string>() { DefaultFirstValue };

            compoundList.AddRange(library.Source);

        }

        public void Print() {

            foreach(string dataValue in compoundList) {

                Console.WriteLine(dataValue);   

            }

        }

    }

    public static void Main()

    {

        DataLibrary library = new DataLibrary();

        DataUser user = new DataUser(library);

        user.Print();

    }

}