[C#] Hjälp med array

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Zoomware.Examples.Collections16
{
    class Program
    {
        static void Main ( string [ ] args )
        {
            List<StringLookup> list = new List<StringLookup> ( );

            list.Add ( new StringLookup ( ) );
            list.Add ( new StringLookup ( ) );

            list [ 0 ] [ "name" ] = "kalle";
            list [ 0 ] [ "nick" ] = "kamel";

            list [ 1 ] [ "name" ] = "pekz";
            list [ 1 ] [ "description" ] = "visar ett exampel";

            foreach ( StringLookup lookup in list )
                Console.WriteLine ( lookup.ToString ( ) );

            Console.ReadKey ( );
        }
    }

    class StringLookup
    {
        public StringLookup ( )
        {
            string [ ] keys = new string [ ] { "name", "nick", "description" };
        }

        public StringLookup ( string [ ] keys )
        {
            foreach ( string key in keys )
                holder.Add ( key, string.Empty );

        }

        public string this [ string key ]
        {
            get { return holder [ "key" ]; }
            set
            {
                if ( holder.ContainsKey ( key ) )
                    holder [ key ] = key;
                else
                    holder.Add ( key, value );
            }
        }

        public override string ToString ( )
        {
            StringBuilder sb = new StringBuilder ( );

            foreach ( string key in holder.Keys )
                sb.AppendLine ( string.Format ( "key: {0}, value: {1}", key, holder [ key ] ) );

            return sb.ToString ( );
        }

        private Dictionary<string, string > holder = new Dictionary<string, string> ( );
    }
}

user usr = lista[index];
usr.Namn = "Nytt värde";
lista[index] = usr;