How does dictionary works in c#


In C#, the `Dictionary<TKey, TValue>` class is used to implement a dictionary, which is essentially a type of hashtable. Here's a breakdown of how the `Dictionary<TKey, TValue>` works:

1. Key-Value Storage:
   - A `Dictionary<TKey, TValue>` stores data in key-value pairs.
   - Each key in the dictionary must be unique.

2. Hash Function:
   - Internally, the dictionary uses a hash function to convert the key into an index in the underlying array.
   - This enables quick retrieval of values based on their keys.

3. Array Storage:
   - The dictionary maintains an internal array to store the key-value pairs.
   - The index for each key is determined by the hash function.

4. Collision Handling:
   - Like other hashtables, the `Dictionary` class must handle collisions, where multiple keys hash to the same index.
   - It typically uses techniques like chaining (linked lists at each index) or open addressing.

5. Addition and Retrieval:
   - When you add a key-value pair using `Add` or `[]` notation, the hash function determines the index, and the pair is stored at that location.
   - When you retrieve a value using a key, the hash function is applied again to find the index, and the value is retrieved.

Here's an example of using `Dictionary<TKey, TValue>`:


using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        // Creating a dictionary with string keys and int values
        Dictionary<string, int> myDictionary = new Dictionary<string, int>();

        // Adding key-value pairs
        myDictionary.Add("one", 1);
        myDictionary["two"] = 2; // Using indexer for adding/updating

        // Retrieving values
        int value = myDictionary["one"];
        Console.WriteLine("The value for key 'one' is: " + value);
    }
}


In this example, the `Dictionary` class takes care of the details of hashing, collision resolution, and provides methods for adding, removing, and retrieving key-value pairs efficiently.

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