SharpDevelop is a free and open source
IDE for the C#, Visual Basic .NET (VB.NET), Boo, and (starting from version 3.0) F# andIronPython programming languages.
Microsoft's Visual Studio .NET. Early in its development there was a fork to Mono/Gtk# calledMonoDevelop which includes multi-platform support.
SharpDevelop uses its own parsers for C# and VB.NET code completion. The parsers were generated using a grammar description and a modified version of the Coco/R compiler generator of the University of Linz, which is included in the source code. For Boo, the parser from the Boo compiler is used but resolving the type of expressions and type inference is done with custom code that supports lazy evaluation of the types. SharpDevelop 1.1 can import projects written with Visual Studio and SharpDevelop 2.0 can open and edit them directly. It also can translate whole projects from VB.NET to C# and vice-versa.
SharpDevelop 2.0 has an integrated debugger. It uses its own debugging library that communicates with the Microsoft .NET runtime using COM interop.
While SharpDevelop 2.0 uses the same MSBuild project files as Visual Studio, it is still able to use other .NET compilers such as older framework versions (1.0, 1.1) or the Mono compiler.
Source Information: Wikipedia