Questions tagged [c#]

c# is a multi-paradigm programming language including object-oriented programming, functional programming, and imperative programming created by Microsoft in conjunction with .NET. C# can be used with any .NET implementation such as .NET, .NET Framework, Mono, ML.Net and Xamarin.

Versions

¹: Language specification

²: Specification proposal

New features

Versions 1.0/1.2 and 2.0 of C# were submitted and approved as both ECMA (Web-Version) and ISO/IEC standards. Latest ECMA version matches Microsoft C# 5.0 specification. Language specifications are also available from Microsoft for C# 3.0 and C# 5.0 as well as C# 6.0 draft.

The language's type system was originally static, with only explicit variable declarations allowed. The introduction of var (C# 3.0) and dynamic (C# 4.0) allowed it to use type inference for implicit variable typing, and to consume dynamic type systems, respectively. Delegates, especially with lexical closure support for anonymous methods (C# 2.0) and lambda expressions (C# 3.0), allow the language to be used for functional programming.

C# 5.0 introduced the async and await keywords to simplify the use of asynchronous function calls.

C# 6.0 introduced the null propagation operator ?., exception filters, string interpolation, and many other features that help to write simple code.

C# 7.0 introduced multiple out arguments, pattern matching, tuples for a return value, is-expressions & switch statements with patterns, deconstruction, local functions, and some more.

C# 7.1 introduced generic Pattern Matching, inferred tuple element names, default literal expressions, async main, and some more.

C# 7.2 introduced private protected, non-trailing named arguments, digital separator after base specifier, ref conditional expression, reference semantics for value types, and some more.

C# 7.3 introduced features that enable safe code to be as performant as unsafe code, new compiler options, the usage of out variable declarations in field, property and constructor initializers, support == and != on tuple types and some more.

C# 8.0 introduced nullable reference types which generates compiler warnings about possible dereferencing of nulls unless the code expresses explicitly that a variable may be null (e.g., string? foo is a variable which may be null), async streams which empowers -especially- IoT and cloud integrations and default interface methods to prevent breaking changes to interfaces, along with some other improvements.

C# 9.0 introduced plenty of new concepts and features such as Records, Init only setters, Top-level statements, Pattern matching enhancements and more.

The compilation is usually done in the Microsoft Intermediate Language (MSIL), which is then JIT-compiled to native code (and cached) during execution in the Common Language Runtime (CLR). However, options like NGen (for the .NET Framework) and AOT (for Mono) mean that C# code can be directly compiled into the native image. Additionally, some frameworks (for example, the .NET Micro Framework) act as CIL interpreters, with no JIT.

Generics in C# are provided in part by the runtime, unlike C++ templates (templates are resolved at compile time), or Java's generics (which use type-erasure).

With the combination of .NET Core for Windows, macOS and Linux, .NET Framework for Windows (desktop/server/mobile), Mono that powers Xamarin applications on Android, Mac, iOS, tvOS and watchOS, Silverlight/Moonlight (browser/mobile), Compact Framework (mobile), and Micro Framework (embedded devices), it's available for a wide range of platforms.

C# 10 introduced file-scoped namespace declarations, global using directives, implicit usings, record structs, along with some other improvements.

C# 11 introduced raw string literals, required members, generic attributes, list patterns, file-local types, generic math support and more.

Hello World Example:

using System;

class Hello
{
    static void Main()
    {
        Console.WriteLine("Hello, World!");
    }
}

Hello World example using classes:

using System;

namespace HelloWorldUsingClasses
{
    class Greeting
    {
        public static void SayHello()
        {
            Console.WriteLine("Hello World!");
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Greeting.SayHello();
        }
    }
}

Hello World example since .NET 6:

// See https://aka.ms/new-console-template for more information
Console.WriteLine("Hello, World!");

Stack Overflow resources

• Chat room for C#

FAQs

• How to send email in ASP.NET C#
• What are the correct version numbers for C#?
• What is the difference between String and string in C#?
• Why is Random giving the same results every time?
• Captured variables in loops
• In C#, is it possible to cast a List<Child> to List<Parent>?
• Does C# pass objects by reference?
• Why does the compiler complain about my conditional expression (a == b ? x : y)?
• Why do I get a NullReferenceException? (Object reference not set to instance of object)
• What is an "index out of range" exception, and how do I fix it?
• Hidden Features of C#?

Release Notes

• New Features in C# (Latest)
• New Features in C# 4
• New Features in C# 6
• New Features in C# 7
• New Features in C# 8
• New Features in C# 9
• New Features in C# 10
• New Features in C# 11
• What's new in the .NET Framework?

Resources

• The history of C#
• C# 5.0 Language Specification
• C# 6.0 draft Language Specification
• Wikipedia Article
• .NET Projects on GitHub
• Eric Lippert's old blog || Eric Lippert's new blog
• Jon Skeet's blog
• Programming Guide
• Getting Started with Visual C#
• C# Fundamentals: Development for Absolute Beginners
• Visual C# .NET for Beginners
• csharp.2000things
• Dot Net Perls

Books

• CLR via C#
• C# 9.0 in a Nutshell: The Definitive Reference
• C# in Depth
• Head First C# (3rd Edition, 4th Edition)
• The C# Programming Language (3rd Edition, 4th Edition)
• Framework Design Guidelines (2nd Edition, 3rd Edition)
• Essential C# (6.0 (5th Edition), 7.0 (6th Edition), 8.0 (7th Edition))
• Visual C# How to Program
• Visual C# .NET Step by Step
• C# 5.0 Unleashed
• Pro C# (7.0 (8th Edition), 8.0 (9th Edition), 9.0 (10th Edition))
• Learning C# 3.0
• Starting out with Visual C# (4th Edition, 5th Edition)
• Programming C# (5.0, 8.0)
• C# 4.0 The Complete Reference
• C# Design Pattern Essentials
• C# 6.0 and the .NET 4.6 Framework
• C# 7 and .NET Core
• Effective C# (Covers C# 6.0), 50 Specific Ways to Improve Your C# (3rd Edition)
• C# 7 Quick Syntax Reference: A Pocket Guide to the Language, APIs, and Library (2nd Edition)

Tutorials

• MSDN
• Microsoft Virtual Academy
• learn.microsoft.com
• microsoft.com/dotnet
• Pluralsight C# path
• exercism.org

Future of C# language

• Language Feature Status

Contribute and propose new features here.

Demo Projects

• CodePlex
• GitHub

C# Online IDE

• Repl C#
• .NET Fiddle
• rextester.com

C# Offline IDE

• Visual Studio Code
• Visual Studio
• Visual Studio for Mac
• JetBrains Rider

Related tags

• c#-2.0
• c#-3.0
• c#-4.0
• c#-5.0
• c#-6.0
• c#-7.0
• c#-7.1
• c#-7.2
• c#-7.3
• c#-8.0
• c#-9.0
• c#-10.0
• c#-11.0