Dictionary questions

[prixone]

Hi,

this is just a sample gathered from elsewhere where i would like to go for a few doubts.

To begin with you need 2 args on the Dictionary, key and value, but even so does it still store the data Enumerated (like "key cat, value 2" is stored on position 0) ?

What would be the best approch to Enumerate my data ?
Some way to reuse empty positions, for example, i have 10 items on it, but item 5 is null so the best way would be going thru all data to actually know that 5 is null (considering ofc u dont know it) and fill it up with some other data ? or is there an easier way of doing it (like just using d.Add(data,data) it would take in place on the null item, for example) ?

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        // Example Dictionary again
        Dictionary<string, int> d = new Dictionary<string, int>()
        {
            {"cat", 2},
            {"dog", 1},
            {"llama", 0},
            {"iguana", -1}
        };
        // Loop over pairs with foreach
        foreach (KeyValuePair<string, int> pair in d)
        {
            Console.WriteLine("{0}, {1}",
                pair.Key,
                pair.Value);
        }
        // Use var keyword to enumerate dictionary
        foreach (var pair in d)
        {
            Console.WriteLine("{0}, {1}",
                pair.Key,
                pair.Value);
        }
    }
}