ASP. NET is an open source web framework originally released by Microsoft in January 2002 with the first iteration of the .NET framework. It is built on the Common Language Runtime (CLR), allowing the use of any .NET language including C# (object-oriented), F# (functional first), VB. NET (a legacy of Visual Basic, used widely by about ten million coders between 1991 and 2001), and less frequently, C++, and CLI implementations of Python and Ruby.