C# Tutorial 5.3: Dictionaries

 A dictionary in C# is a collection of key-value pairs, where each key must be unique. It provides fast lookup and retrieval of values based on their associated keys. Here's a basic tutorial on using dictionaries in C#:

Creating a Dictionary

To use dictionaries in C#, you need to include the System.Collections.Generic namespace. Dictionaries are part of this namespace. You can create a dictionary using the Dictionary<TKey, TValue> class, where TKey is the type of the keys, and TValue is the type of the values.

using System;

using System.Collections.Generic;

class Program

{

    static void Main()

    {

        // Creating a dictionary with int keys and string values

        Dictionary<int, string> myDictionary = new Dictionary<int, string>();

        // Adding key-value pairs

        myDictionary.Add(1, "One");

        myDictionary.Add(2, "Two");

        myDictionary.Add(3, "Three");

        // Accessing values using keys

        Console.WriteLine(myDictionary[1]);  // Output: One

        // Iterating through key-value pairs

        foreach (var kvp in myDictionary)

        {

            Console.WriteLine($"Key: {kvp.Key}, Value: {kvp.Value}");

        }

    }

}

Dictionary Initialization

You can also initialize a dictionary with values directly:

Dictionary<int, string> myDictionary = new Dictionary<int, string>

{

    {1, "One"},

    {2, "Two"},

    {3, "Three"}

};

Checking if a Key Exists

Before accessing a value using a key, it's a good practice to check if the key exists to avoid exceptions:

int keyToCheck = 4;

if (myDictionary.ContainsKey(keyToCheck))

{

    Console.WriteLine($"Value for key {keyToCheck}: {myDictionary[keyToCheck]}");

}

else

{

    Console.WriteLine($"Key {keyToCheck} not found");

}

Removing Items

You can remove items from a dictionary using the Remove method:

myDictionary.Remove(2); // Removes the key-value pair with key 2

Dictionary Methods

Dictionaries provide various methods for manipulation, such as ContainsKey, ContainsValue, Clear, Count, etc. Refer to the official documentation for a comprehensive list.

Dictionaries are a powerful data structure in C#, and they are commonly used when fast lookups based on keys are required.