Get an ICollection containing the keys in the Hashtable in CSharp

/*from   ww w  .j a  v a2  s  .c o  m*/
using System;
using System.Collections;

class MainClass
{
    public static void Main()
    {
        Hashtable    hash = new Hashtable();
        hash["A"] = "1";
        
        foreach (string firstName in hash.Keys)
        {
            Console.WriteLine("{0} {1}", firstName, hash[firstName]);
        }
    }
}