Microsoft Visual C# is Microsoft's implementation of the C# specification, included in the Microsoft Visual Studio suite of products. It is based on the ECMA/ISO specification of the C# language, which Microsoft also created. While multiple implementations of the specification exist, Visual C# is by far the one most commonly used. In most contexts, an unqualified reference to "C#" is taken to mean "Visual C#."
Visual C# is currently used in development of Windows and Xbox Live games via Microsoft XNA, which allows game developers to create and share their games with other gamers. Visual C# is also heavily used by ASP.NET web sites and standalone applications based on the .NET Framework. Note: As of October 2012 Microsoft has ended support and future releases of XNA.