CodeUtility
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Online C# Compiler & Debugger

Write, compile, run, and debug C# code online. Set breakpoints, step into or over code, and inspect variables and nested objects in a full IDE with multiple files, saved workspaces, sharing, and live collaboration—no setup required.

Pre-installed Libs
🚀 350,749 total executions (3 this month)
Output

Practice C# with coding challenges

Solve hands-on problems right in this editor: run the sample tests, submit, and get an AI code review.

All C# challenges
Easy

Average of Three

Average three whole numbers.

You'll learn ArithmeticDivision
BeginnerLearning-pathVariables
Python C++ C#
1 solved
View solutions (1)
Easy

Rectangle Perimeter

Compute the perimeter of a rectangle from its sides.

You'll learn ArithmeticReturn values
BeginnerLearning-pathVariables
Python C++ C#
1 solved
View solutions (1)
Medium

One Generation of a Genetic Algorithm

Breed the next generation of bit strings with tournament selection, single-point crossover and mutation.

You'll learn Genetic algorithmsEvolutionary search
OptimizationSimulationai
Python C++ C#
0 solved
No solutions yet
Easy

Epsilon-Greedy Multi-Armed Bandit

Balance exploration and exploitation on a multi-armed bandit with epsilon-greedy action selection.

You'll learn Explore vs exploitBandits
Reinforcement learningaimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Markov Chain State Distribution

Propagate a probability distribution through a Markov chain's transition matrix for a number of steps.

You'll learn Markov chainsProbability
Simulationaimath
Python C++ C#
0 solved
No solutions yet
Medium

Value Iteration

Compute how valuable each state of a Markov decision process is by repeatedly applying the Bellman optimality update.

You'll learn Bellman equationMDPs
Reinforcement learningaimachine learning
Python C++ C#
0 solved
No solutions yet
Medium

Q-Learning Updates

Apply the Q-learning update to a stream of experiences and watch rewards flow back to earlier states.

You'll learn Q-learningDiscounted rewards
Reinforcement learningaimachine learning
Python C++ C#
0 solved
No solutions yet
Medium

Alpha-Beta Pruning

Evaluate a game tree with minimax and alpha-beta pruning, and count how many leaves the search really looks at.

You'll learn Alpha-beta pruningGame search
RecursionTreesai
Python C++ C#
0 solved
No solutions yet
Medium

Minimax Tic-Tac-Toe

Pick the perfect tic-tac-toe move by searching the whole game tree with minimax.

You'll learn MinimaxGame trees
Recursionai
Python C++ C#
0 solved
No solutions yet
Medium

A* Search on a Weighted Grid

Find the cheapest path across a grid of terrain costs with A*, the search algorithm behind game and robot pathfinding.

You'll learn A* searchHeuristics
GraphsGridsShortest-pathai
Python C++ C#
0 solved
No solutions yet
Medium

Temperature and Top-K Sampling

Choose the next token like a language model does: keep the top k logits, apply temperature, and sample.

You'll learn Text generationSampling
aimachine learning
Python C++ C#
0 solved
No solutions yet
Hard

Multi-Head Self-Attention

Project the input into queries, keys and values, run attention in several heads in parallel, and combine them.

You'll learn Multi-head attentionMatrix projections
aimachine learning
Python C++ C#
0 solved
No solutions yet

🔷 About This C# / .NET Online Executor

The CodeUtility C# Executor lets you write and run real C# code directly in your browser - no installation, Visual Studio setup, or .NET SDK required. It’s powered by a secure sandbox that supports the .NET runtime and modern C# language versions, including C# 9 and later.

This tool uses dotnet-script under the hood to compile and execute your code with true .NET behavior, allowing you to experiment with both basic and advanced C# features like LINQ, async/await, pattern matching, and generics.

You can test simple scripts, functions, and logic flows, or explore concepts like classes, structs, inheritance, and interfaces - all in a clean, distraction-free coding environment.

Whether you’re learning C#, testing algorithms, or experimenting with .NET features, the CodeUtility C# Executor gives you a fast, secure, and reliable way to run C# code instantly from any browser.

More than a code runner

Use a multi-file editor, an isolated execution terminal, runtime-specific libraries, persistent workspaces, sharing, and real-time collaboration from the same executor.

How to use this executor?

Choose a runtime, open or create a file, write your code, and select Run. Output appears in the terminal, while signed-in users can keep files in a workspace, install libraries, and collaborate through shares.

  1. Select a version and edit the current file or open another workspace file.
  2. Run the code, provide input in the terminal when requested, and review saved run history.
  3. Use libraries, workspace tools, sharing, and chat when your task needs more than one snippet.

💡 C# Basics & Examples You Can Try Above

1. Declaring Variables and Constants

C# uses strongly-typed variable declarations. Use const for compile-time constants and readonly for runtime constants. 

int age = 30;
double pi = 3.14159;
char grade = 'A';
string name = "Alice";
bool isActive = true;

// Constants
const int MaxUsers = 100;
const string Company = "CodeUtility";

2. Conditionals (if / switch)

Use if, else if, and switch for control flow.

int x = 2;
if (x == 1)
{
    Console.WriteLine("One");
}
else if (x == 2)
{
    Console.WriteLine("Two");
}
else
{
    Console.WriteLine("Other");
}

switch (x)
{
    case 1:
        Console.WriteLine("One");
        break;
    case 2:
        Console.WriteLine("Two");
        break;
    default:
        Console.WriteLine("Other");
        break;
}

3. Loops

C# supports for, while, and foreach loops.

for (int i = 0; i < 3; i++)
{
    Console.WriteLine(i);
}

int n = 3;
while (n > 0)
{
    Console.WriteLine(n);
    n--;
}

4. Arrays

Arrays store fixed-size collections of elements of the same type.

int[] numbers = { 10, 20, 30 };
Console.WriteLine(numbers[1]);

5. List Manipulation

Use List<T> for dynamic collections.

List<int> nums = new List<int> { 1, 2, 3 };
nums.Add(4);
nums.Remove(2);

foreach (int n in nums)
{
    Console.Write(n + " ");
}

6. Console Input/Output

Use Console.WriteLine and Console.ReadLine for basic I/O.

Console.Write("Enter your name: ");
string name = Console.ReadLine();
Console.WriteLine($"Hello, {name}!");

7. Functions

Define methods using a return type, name, and parameters.

int Add(int a, int b)
{
    return a + b;
}

Console.WriteLine(Add(3, 4));

8. Dictionaries

Dictionary<TKey, TValue> stores key-value pairs.

Dictionary<string, int> ages = new Dictionary<string, int>();
ages["Alice"] = 30;
Console.WriteLine(ages["Alice"]);

9. Exception Handling

Handle runtime errors using try, catch, and finally.

try
{
    throw new Exception("Something went wrong");
}
catch (Exception ex)
{
    Console.WriteLine(ex.Message);
}

10. File I/O

Use File and StreamReader/StreamWriter for file operations.

File.WriteAllText("file.txt", "Hello File");
string text = File.ReadAllText("file.txt");
Console.WriteLine(text);

11. String Manipulation

C# strings support methods like Length, Substring, Contains.

string message = "Hello World";
Console.WriteLine(message.Length);
Console.WriteLine(message.Substring(0, 5));
Console.WriteLine(message.Contains("World"));

12. Classes & Objects

C# supports object-oriented programming through classes and objects.

class Person
{
    public string Name;
    public Person(string name) => Name = name;
    public void Greet() => Console.WriteLine($"Hi, I'm {Name}");
}

Person p = new Person("Alice");
p.Greet();