Dictionary questions

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) ?

Code:

---

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);
        }
    }
}

---

Quote:

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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) ?

---

I'm not sure about that. All I would say on that point is that is a dictionary not an array where you can index by position.

Quote:

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What would be the best approch to Enumerate my data ?

---

The sample you have shows you the best way to enumerate through the data.

Quote:

---

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) ?

---

There isn't any null item as such. You have key value pairs. You may choose to put a null value against a particular key. You would have to iterate through the dictionary to see which keys have null values stored against. I would also mention at this point that not every dictionary will allow null values (e.g. Dictionary<String, Int32>). Think of it as a dictionary a collection of key,value pairs.

Code:

---

private void Test()
{
  var test = new Dictionary<String, Int32>();
 
  // The line below will set the value 35 against the key A. If the key doesn't exist it will
  // be  created and initialised with the value 35.
  test["A"] = 35;

  var test2 = new Dictionary<String, String>();
 
  // You can also use the Add method to add entries into the dictionary. Each entry is a
  // key value pair. You cannot have a null value unless you actually specify (if the definition
  // of the dictionary permits it)
  test2.Add("A", null);
}

---

Hope this helps.

Quote:

---

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) ?

---

Nope. The documentation explicitly states that the keys are not in any specific order.

Quote:

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What would be the best approch to Enumerate my data ?

---

If you need to enumerate the keys in the same order you add them to your container, use a List<> or something similar.

Thanks for the replies.

Nelo yes that is what i currently do, my own keys etc i was just trying to find out this information to make sure that was the way to go.