Run C# online

C# is Microsoft's cross-platform, statically-typed language and the workhorse of the .NET ecosystem — Unity games, Blazor web apps, enterprise services, cloud functions. Modern C# is fast, expressive, and — since .NET Core — genuinely first-class on Linux.

ls-judge runs C# via the real `dotnet` CLI inside a Firecracker microVM. Choose the language version (12, 13, 14) and get the matching .NET runtime.

Bring a single file (Program.cs) or a multi-file project. Top-level statements work; so does an explicit `Main`. Stdin from the Test panel maps to Console.In.

What you get in C#

Clicking "Run now" opens the playground with this exact code and a matching test case pre-loaded — passes on first Run.

using System;
class Solution { static void Main() { int n = int.Parse(Console.ReadLine()!.Trim()); Console.WriteLine(n * 2); } }

Common questions about C# on ls-judge

Which .NET SDK is under C# 14?

.NET 9 — the SDK that ships C# 13; C# 14 uses the current preview SDK where required.

Can I add NuGet packages?

Not on the free tier — the sandbox has no network egress to nuget.org. Bring source only.

Does the runner support top-level statements?

Yes — Program.cs with just `Console.WriteLine("hi");` compiles and runs.

Is Rider / VS integration possible?

Use their SSH remote-run features against your own machine; this playground is browser-first.

• C# language reference↗
• .NET documentation↗