C# (C-sharp)

What C# is

C# (“C-sharp”) is a statically-typed, object-oriented language created by Microsoft and first released in 2000. It is compiled, garbage-collected, and strongly tooled, and today it is fully cross-platform: the same C# runs on Windows, macOS, and Linux, and targets web, desktop, cloud, mobile, and games (it’s the language of the Unity engine). It pairs C-family syntax with high-level features that keep it productive without dropping to manual memory management.

C# & .NET

A common point of confusion: C# is the language; .NET is the platform it runs on. You write C#, the compiler turns it into an intermediate language (IL), and the .NET runtime (the CLR) executes that IL, compiling it to native code just in time. .NET also provides the standard library and tooling. Modern .NET (the successor to the Windows-only .NET Framework) is open-source and cross-platform; other languages like F# target the same runtime.

Signature features

• Strong, static typing with rich type inference (var) and, since C# 8, nullable reference types that surface null bugs at compile time.
• LINQ: declarative queries (filter/project/group/join) over any sequence with one syntax.
• async/await: non-blocking asynchronous code that reads sequentially.
• Generics: type-safe reusable containers and algorithms without casting.
• Records & value types: concise immutable data types with value equality.
• Properties, pattern matching, and first-class delegates/events for clean object-oriented and event-driven code.

In code

// Modern C#: records, LINQ, async/await, nullable reference types
public record Dev(string Name, int CommitsThisYear);

var team = new List<Dev> {
    new("Ada", 412),
    new("Linus", 1290),
    new("Grace", 88),
};

// LINQ: declarative queries over any sequence
var prolific = team
    .Where(d => d.CommitsThisYear > 100)
    .OrderByDescending(d => d.CommitsThisYear)
    .Select(d => d.Name);

// async/await: non-blocking I/O without callbacks
async Task<string> FetchAsync(HttpClient http, string url) {
    return await http.GetStringAsync(url);   // frees the thread while waiting
}

C# vs Java vs C++

Coming from C++? The memory model is the biggest shift, see smart pointers & RAII and memory leaks for what the garbage collector handles for you. The OOP concepts and design patterns carry straight over.

FAQ