Collections (Dictionary)

Relax. We'll talk through this in plain words — no textbook voice.

Dictionary<TKey, TValue> is a collection that stores data as key-value pairs. Because keys and values are paired together, it's great for mapping data like username to role, product code to price, or country to capital.

csharp

using System;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args)
    {
        Dictionary<string, int> productPrices = new Dictionary<string, int>();

        productPrices.Add("Laptop", 1200);
        productPrices.Add("Mouse", 25);
        productPrices.Add("Keyboard", 80);

        Console.WriteLine(productPrices["Laptop"]);

        if (productPrices.ContainsKey("Mouse"))
        {
            Console.WriteLine($"Mouse price: {productPrices["Mouse"]}");
        }
    }
}

Watch out for this

productPrices["Laptop"] uses the key to fetch the value.
Accessing a key that doesn't exist can throw an error. That's why it's safer to check first with ContainsKey().
Dictionary keys must be unique. Adding a duplicate key can cause an error.

You should see

1200 Mouse price: 25