C# is a multi-paradigm programming language encompassing strong typing, imperative, declarative, functional, generic, object-oriented (class-based), and component-oriented programming disciplines. It was developed by Microsoft within its .NET initiative and later approved as a standard by Ecma (ECMA-334) and ISO (ISO/IEC 23270:2006). C# is one of the programming languages designed for the Common Language Infrastructure.

C# is a general-purpose, object-oriented programming language. Its development team is led by Anders Hejlsberg. The most recent version is C# 6.0 which was released in 2015.

Design goals

The ECMA standard lists these design goals for C#:

  • The C# language is intended to be a simple, modern, general-purpose, object-oriented programming language.
  • The language, and implementations there of, should provide support for software engineering principles such as strong type checking, array bounds checking, detection of attempts to use uninitialized variables, and automatic garbage collection. Software robustness, durability, and programmer productivity are important.
  • The language is intended for use in developing software components suitable for deployment in distributed environments.
  • Portability is very important for source code and programmers, especially those already familiar with C and C++.
  • Support for internationalization is very important.
  • C# is intended to be suitable for writing applications for both hosted and embedded systems, ranging from the very large that use sophisticated operating systems, down to the very small having dedicated functions.
  • Although C# applications are intended to be economical with regard to memory and processing power requirements, the language was not intended to compete directly on performance and size with C or assembly language.


During the development of the .NET Framework, the class libraries were originally written using a managed code compiler system called Simple Managed C (SMC). In January 1999, Anders Hejlsberg formed a team to build a new language at the time called Cool, which stood for “C-like Object Oriented Language”. Microsoft had considered keeping the name “Cool” as the final name of the language, but chose not to do so for trademark reasons. By the time the .NET project was publicly announced at the July 2000 Professional Developers Conference, the language had been renamed C#, and the class libraries and ASP.NET runtime had been ported to C#.

C#’s principal designer and lead architect at Microsoft is Anders Hejlsberg, who was previously involved with the design of Turbo Pascal, Embarcadero Delphi (formerly CodeGear Delphi, Inprise Delphi and Borland Delphi), and Visual J++. In interviews and technical papers he has stated that flaws[citation needed] in most major programming languages (e.g. C++, Java, Delphi, and Smalltalk) drove the fundamentals of the Common Language Runtime (CLR), which, in turn, drove the design of the C# language itself.

James Gosling, who created the Java programming language in 1994, and Bill Joy, a co-founder of Sun Microsystems, the originator of Java, called C# an “imitation” of Java; Gosling further said that “[C# is] sort of Java with reliability, productivity and security deleted.” Klaus Kreft and Angelika Langer (authors of a C++ streams book) stated in a blog post that “Java and C# are almost identical programming languages. Boring repetition that lacks innovation,” “Hardly anybody will claim that Java or C# are revolutionary programming languages that changed the way we write programs,” and “C# borrowed a lot from Java – and vice versa. Now that C# supports boxing and unboxing, we’ll have a very similar feature in Java.” In July 2000, Anders Hejlsberg said that C# is “not a Java clone” and is “much closer to C++” in its design.

Since the release of C# 2.0 in November 2005, the C# and Java languages have evolved on increasingly divergent trajectories, becoming somewhat less similar. One of the first major departures came with the addition of generics to both languages, with vastly different implementations. C# makes use of reification to provide “first-class” generic objects that can be used like any other class, with code generation performed at class-load time. Furthermore, C# has added several major features to accommodate functional-style programming, culminating in the LINQ extensions released with C# 3.0 and its supporting framework of lambda expressions, extension methods, and anonymous types. These features enable C# programmers to use functional programming techniques, such as closures, when it is advantageous to their application. The LINQ extensions and the functional imports help developers reduce the amount of “boilerplate” code that is included in common tasks like querying a database, parsing an xml file, or searching through a data structure, shifting the emphasis onto the actual program logic to help improve readability and maintainability.

C# used to have a mascot called Andy (named after Anders Hejlsberg). It was retired on January 29, 2004.

C# was originally submitted to the ISO subcommittee JTC 1/SC 22 for review, under ISO/IEC 23270:2003, was withdrawn and was then approved under ISO/IEC 23270:2006.