CSharpRepl is the best interpreter for C#

CSharpRepl is a tool that allows us to run C# code interactively in a REPL console (Read-Eval-Print Loop).

CSharpRepl provides an interactive console where you can write and execute snippets of C# code in real time (that is… you know the Python or Nodejs interpreter? Well, it’s something like that for C#).

This tool is very useful for performing quick tests, experimenting with new ideas, and debugging code without needing to compile and run a full application.

Something that, in my opinion, Microsoft itself should provide. But hey, since they’re not… the community to the rescue!

Installation and Configuration

You can install CSharpRepl globally on your system using the .NET CLI:

2. Verify Installation

Once installed, verify the installation by running the following command in your terminal:

You should see an interactive CSharpRepl console ready to accept commands.

Integrate with Windows Terminal

In general, the preferred way to use C# Repl is from Windows Terminal, like any other command interpreter. To do this, you need to add it to the configuration file. Go to “Options” and at the bottom left, click “Open Json File”.

There, in the profiles\list collection, add this:

Now, from Windows Terminal, C# Repl appears in the dropdown options.

How to Use CSharpRepl

Run C# Code

In the CSharpRepl console, you can write any C# code snippet and get immediate results. Here are some basic examples:

Print a Message

Console.WriteLine("Hello, CSharpRepl!");

Declare and Use Variables

int x = 10;
int y = 20;
Console.WriteLine(x + y);

Define and Call Methods

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

Console.WriteLine(Add(5, 7));

Advanced Usage

CSharpRepl also allows the use of more advanced C# features, such as creating classes, using LINQ, and working with external libraries.

Create a Class

class Person
{
   public string Name { get; set; }
   public int Age { get; set; }
}

var person = new Person { Name = "John", Age = 30 };
Console.WriteLine($"Name: {person.Name}, Age: {person.Age}");

Use LINQ

var numbers = new List<int> { 1, 2, 3, 4, 5 };
var evens = numbers.Where(n => n % 2 == 0);
foreach (var even in evens)
{
   Console.WriteLine(even);
}

Load and Use External Libraries

You can load assemblies and use external libraries directly in the REPL console. For example, to use a JSON library:

#r "path/to/Newtonsoft.Json.dll"
using Newtonsoft.Json;

var json = JsonConvert.SerializeObject(new { Name = "John", Age = 30 });
Console.WriteLine(json);

Or NuGet packages

#r "nuget: Dumpify"
using Newtonsoft.Json;

var json = JsonConvert.SerializeObject(new { Name = "John", Age = 30 });
Console.WriteLine(json);

Run CSX Files

We can also create .csx files with a series of instructions or a script to run sequentially. For example,

var a = 2 + 2;
Console.WriteLine(a);

Now to run it we simply do:

and C# Repl will execute all the lines one by one.