What Is C#? A Complete Guide to the C# Language in 2026

Updated October 2026 

TL;DR: C# (pronounced C sharp) is a modern, object-oriented, strongly typed programming language created by Microsoft and the main language of the .NET platform. It is free, open source and cross-platform. In the 2025 Stack Overflow Developer Survey, 29.9% of professional developers reported using it. The latest version, C# 14, shipped with .NET 10 in November 2025.

Choosing a programming language is rarely just a technical decision. It shapes how fast your team delivers, how easy it is to hire, how much your systems cost to maintain and how long they stay supported. C# sits at the center of many of these decisions, especially in companies that run on Microsoft technologies, build enterprise systems or maintain applications that have been in production for years.

This guide explains what C# is, what it is used for, what changed with C# 14 and .NET 10, how it compares with Java and Python, and how to decide whether it is the right choice for your next software project.

What is C#?

C# is a general-purpose programming language developed by Microsoft and used to build web, cloud, desktop, mobile and game applications on the .NET platform. According to Microsoft Learn, it is the most popular language for .NET, a free, cross-platform and open-source development environment.

The name comes from music: the sharp sign (♯) raises a note by a semitone, suggesting a step up from the C family of languages. Developers who know C, C++, Java, JavaScript or TypeScript will recognize much of its syntax, including braces, semicolons and familiar control structures.

C# is primarily object-oriented, but it also incorporates features from functional programming. It is strongly typed, which means the compiler checks data types before the program runs and catches many errors early. It is standardized as ECMA-334 and ISO/IEC 23270.

A brief history of C#

C# was created by a team led by Anders Hejlsberg (also the designer of Turbo Pascal and Delphi, and later TypeScript). The language has evolved steadily, usually adding features that make code shorter, safer and faster.

C# vs .NET: what’s the difference?

C# is the language; .NET is the platform that runs it. The platform includes the runtime (the Common Language Runtime, or CLR, which executes the code and manages memory), a large set of standard libraries and the tools used to build, test and deploy applications.

It is also important to distinguish between two generations of the platform:

• .NET Framework: the original version, released in 2002, which runs only on Windows. Many corporate systems still depend on it.
• Modern .NET (formerly .NET Core): the current, cross-platform version, which runs on Windows, Linux and macOS, in containers and in the cloud.

For companies, this distinction matters. A system built on the legacy .NET Framework works, but it is harder to scale in the cloud, harder to staff (many developers prefer modern stacks) and cut off from most of the platform’s recent performance gains.

What is C# used for?

C# is used for almost every type of software, but its strongest areas are web applications, APIs and enterprise backend systems. The JetBrains State of .NET 2025 report shows that ASP.NET Core is used by 70% of .NET web developers and that half of all respondents work on backend services.

Web applications and APIs

ASP.NET Core is the main framework for building websites, web applications and REST APIs in C#. In the 2025 Stack Overflow survey, 21.3% of professional developers used ASP.NET Core, and 61.3% of its users said they want to keep working with it. Blazor extends this by allowing teams to build interactive web interfaces in C# instead of JavaScript.

Enterprise and backend systems

ERPs, banking platforms, billing engines, internal portals and integration layers are a natural fit for C#. Strong typing, mature tooling and long-term support releases make it well suited to systems that must run reliably for many years.

Cloud and microservices

C# applications run in containers, on Kubernetes and on serverless platforms such as Azure Functions and AWS Lambda. Integration with Microsoft Azure is especially deep, but nothing ties C# to a single cloud provider.

Desktop applications

Windows Forms, WPF and WinUI are still widely used for internal tools, industrial software and applications that need direct access to local hardware.

Mobile and cross-platform apps

.NET MAUI allows a single C# codebase to target Android, iOS, Windows and macOS, which reduces duplicated effort when the same business logic needs to run on several devices.

Games

C# is the scripting language of Unity, one of the most widely used game engines in the world, which makes it a common entry point for game developers.

Artificial intelligence and data

ML.NET brings machine learning to .NET applications, and Microsoft’s open-source Semantic Kernel lets C# developers integrate large language models and build AI agents into existing enterprise systems.

Knowing what C# can do is the easy part; putting a production system in front of users on time is harder. NextAge’s software projects service provides a dedicated full-stack squad for web, mobile and cloud projects, with scope, deadlines and SLA defined before the first sprint.

Key features of C#

C#’s main strength is the balance between productivity and performance: it is approachable enough for new developers and powerful enough for high-load systems. These are the features that matter most in practice:

• Strong typing: errors are caught at compile time, before they reach production.
• Automatic memory management: a garbage collector frees unused memory, reducing a whole class of bugs common in C and C++.
• LINQ: a single, readable syntax to query collections, databases, XML or JSON.
• Async and await: asynchronous code that reads like sequential code, essential for scalable APIs and services.
• Pattern matching: concise logic for decisions based on the shape and content of data.
• Generics: reusable, type-safe components.
• Records: compact, immutable data models, useful in APIs and domain logic.
• Null safety: nullable reference types help prevent the most common runtime error in many languages.
• Large ecosystem: thousands of open-source packages on NuGet and first-class tools such as Visual Studio, Visual Studio Code and JetBrains Rider.

Getting started has also become simpler. Since C# 14 and .NET 10, a program can live in a single file and run without a project structure:

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

Save it as hello.cs and run dotnet run hello.cs. This makes C# practical for scripts, prototypes and small automation tasks, not only large applications.

What’s new in C# 14 and .NET 10

C# 14 and .NET 10 were released in November 2025, and .NET 10 is a long-term support (LTS) release, supported until November 2028. For companies, the most relevant point is simple: many applications get faster after upgrading, even without rewriting code.

According to the .NET team’s announcement of C# 14, much of the performance improvement in .NET 10 comes from the runtime and core libraries themselves adopting new language capabilities. The main additions are:

• Extension members: the headline feature, which lets teams extend existing types in a more organized and expressive way.
• The field keyword: less boilerplate code when properties need validation or custom logic.
• Implicit span conversions: simpler, faster code for parsing and processing data.
• File-based apps: C# programs that run from a single file, as shown above.

.NET 8 and .NET 9 reach end of support on November 10, 2026

This is the most urgent point for many companies. Microsoft has confirmed that .NET 8 (LTS) and .NET 9 (STS) both reach end of support on November 10, 2026. Applications will keep running after that date, but they will no longer receive security patches or technical support. Microsoft’s recommendation is to move to .NET 10.

In practice, this means:

• Systems on .NET 8 or .NET 9 need a planned upgrade to .NET 10.
• Systems still on the legacy .NET Framework face a larger modernization effort, often the right moment to revisit architecture, cloud strategy and technical debt.
• Security and compliance teams will flag unsupported runtimes in audits and vulnerability scans.

If your systems still run on .NET 8, .NET 9 or the .NET Framework, a structured modernization project lets you move to .NET 10 in planned increments, with defined scope and deadlines, without freezing your product roadmap.

Advantages and disadvantages of C#

C# is a strong choice for long-lived business systems, but it is not the best fit for every scenario. A balanced view helps avoid surprises later.

C# vs Java vs Python

C#, Java and Python are the three languages most often compared in corporate technology decisions. The table below summarizes the main differences:

Source for usage data: Stack Overflow Developer Survey 2025.

A simple rule of thumb: choose C# when your environment relies on Microsoft technologies or you need one stack for web, desktop and mobile; choose Java when your team and infrastructure are already built around the JVM; choose Python when the core of the project is data analysis, machine learning or automation. Many companies combine them, for example a C# backend consuming Python AI services.

When should your company choose C#?

C# is usually the right choice when the project needs reliability, long-term maintainability and integration with corporate systems. Use this checklist to evaluate your scenario:

• Your company already uses Microsoft technologies such as Azure, SQL Server, Microsoft 365 or Power Platform.
• The system will be in production for many years and needs a predictable support cycle.
• Performance, security and strong typing are critical, as in finance, healthcare, logistics or industry.
• You want a single language and team for web, APIs, desktop and mobile.
• You already have .NET systems that need to evolve or be modernized.
• You need to integrate AI capabilities into existing enterprise applications.

If you checked three or more items, C# deserves serious consideration. The next question is usually capacity: who will build and maintain it?

NextAge assembles dedicated squads (developers, QA, DevOps and analysts) for C# and .NET projects. You keep full control of decisions, while we guarantee code quality with AI-assisted code review and a contractual SLA. In 19 years, NextAge has delivered more than 600 projects in 13 countries. Talk to a specialist about your project.

Is C# still worth it in 2026?

Yes. C# remains one of the most used and most stable languages in the market. It has stayed in the top 5 of the TIOBE Index for more than a decade, ranking fifth in September 2026, and was named TIOBE’s Programming Language of the Year in both 2023 and 2025. In the 2025 Stack Overflow survey, 55.8% of developers who use C# said they want to keep using it.

Commenting on the 2025 award, TIOBE CEO Paul Jansen highlighted two major shifts in the language’s trajectory: from Windows-only to cross-platform, and from Microsoft-owned to open source. Those shifts, combined with annual .NET releases, explain why C# continues to be a safe choice for companies.

FAQ

Is C# easy to learn?

Yes, for most people with basic programming knowledge. Its syntax is clear and consistent, and tools such as Visual Studio point out errors as you type. Complete beginners usually find Python faster to start with, but C# teaches concepts (typing, object orientation, asynchronous code) that are valuable in any professional environment.

Is C# only for Windows?

No. Since the launch of .NET Core in 2016, C# applications run on Windows, Linux and macOS, in containers and in any major cloud. Only the legacy .NET Framework and some desktop technologies, such as WPF and Windows Forms, are limited to Windows.

Is C# free and open source?

Yes. The C# compiler, the .NET runtime and its libraries are open source and free to use, including for commercial projects. Paid tools exist, such as some editions of Visual Studio, but free alternatives like Visual Studio Code with the C# Dev Kit are widely used.

What is the difference between C# and .NET?

C# is a programming language; .NET is the platform that runs it, including the runtime, standard libraries and development tools. Other languages also run on .NET, such as F# and Visual Basic, but C# is by far the most popular.

Is C# still relevant in 2026?

Yes. C# ranks fifth in the TIOBE Index (September 2026), was TIOBE’s Language of the Year in 2025 and is used by 29.9% of professional developers, according to the 2025 Stack Overflow survey. Microsoft releases a new version every year.

C# vs Java: which is better for enterprise systems?

Both are excellent for enterprise software and have similar performance and usage among professionals. C# tends to be the better choice in Microsoft and Azure environments; Java is often preferred when the company’s infrastructure and team are already built around the JVM and Spring.

C# vs Python: which should I choose?

Choose C# for high-performance web systems, APIs and long-lived enterprise applications. Choose Python for data science, machine learning and automation. Many companies use both: C# for the core system and Python for analytics or AI services.

What companies use C#?

Microsoft writes most of the .NET runtime and libraries in C#, and Stack Overflow runs on .NET. C# is also widely used in banking, insurance, healthcare, logistics, industry and game studios that build with Unity.

Is C# good for AI and machine learning?

Yes, especially for integrating AI into business applications. ML.NET supports machine learning inside .NET apps, and Semantic Kernel helps developers connect C# systems to large language models and build AI agents. For AI research and model training, Python remains the dominant language.

What is the latest version of C#?

C# 14, released in November 2025 with .NET 10, a long-term support release supported until November 2028. Its main new features are extension members, the field keyword, implicit span conversions and file-based apps.

Conclusion

C# is a mature, high-performance and constantly evolving language, with a predictable support cycle and one of the largest professional communities in the market. For companies, it offers a safe foundation for systems that need to scale and stay in production for years.

The timing also matters: with .NET 8 and .NET 9 reaching end of support on November 10, 2026, this is the moment to plan the next step for your C# applications, whether that means a new product or the modernization of an existing system.

Your next C# project just needs the right squad. Book a free, no-commitment call and leave with a clear plan: team composition, SLA and timeline.