C# (see section on name, pronunciation) is an object-oriented programming language developed by Microsoft as part of the .NET initiative and later approved as a standard by ECMA (ECMA-334) and ISO (ISO/IEC 23270).
#develop (short for SharpDevelop) is a free IDE for C# and
VB.NET projects on Microsoft's .NET platform. It is open-source
(GPL), and you can download both sourcecode and executables