System.Collections.Generic.Dictionary and Possible Exceptions

static void Main(string[] i_args)

{
    Dictionary<string, string> _names = new Dictionary<string, string>
                                            {{"Iliescu", "Ion"}, {"Basescu", "Traian"}
                                            , {null, "Dorel"}}; //ArgumentNullException
    Console.WriteLine(_names[null]); // ArgumentNullException
    Console.WriteLine(_names["Geoana"]); //KeyNotFoundException
}