Lists and Dictionaries in C# - Example You Can Run Online

Introduction

Generic collections preserve type safety and grow dynamically as the program runs.

List<T> maintains order. Dictionary<TKey,TValue> provides fast lookup and TryGetValue avoids exceptions for missing keys.

See how it works

Use the buttons to change the list and watch the indices update. Move start and stop to see which items a slice takes.

Runnable C# example

C#

Run code →

Program.cs

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var scores = new Dictionary<string, int> { ["Ada"] = 95, ["Lin"] = 88 };
        scores["Grace"] = 92;
        if (scores.TryGetValue("Grace", out int score))
            Console.WriteLine(score);
    }
}

Result of running the code

Practice with the debugger

Set a breakpoint on an important assignment or condition, click Debug, and inspect the local values before stepping to the next line.

Practice with a challenge

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