using  System;

using  System.Collections.Generic;

using  System.Linq;

using  System.Text;

namespace  Lookup

{

class  Program

{

static   void  Main( string [] args)

{

Person graham  =   new  Person( " Graham " ,  " Hill " ,  " USA " );

Person emerson  =   new  Person( " Emerson " ,  " Fittipaldi " ,  " USA " );

Person hc  =   new  Person( " Huang " ,  " Cong " ,  " CA " );

List < Person >  listPerson  =   new  List < Person > () { graham, emerson, hc };

Lookup < string , Person >  Persons  =  (Lookup < string , Person > )listPerson.ToLookup(r  =>  r.Counary);

foreach  (Person obj  in  Persons[ " USA " ])

{

Console.WriteLine(obj.FirstName  +   "   " +  obj.LastName);

}

}

}

public   class  Person

{

public   string  FirstName {  get ;  set ; }

public   string  LastName {  get ;  set ; }

public   string  Counary {  get ;  set ; }

public  Person( string  first,  string  last, string  counary)

{

FirstName  =  first;

LastName  =  last;

Counary  =  counary;

}

}

}