.Net/Link

".NET/Link is a toolkit that integrates Mathematica and the Microsoft .NET Framework. It lets you call code written in any .NET-compatible language from Mathematica in a completely transparent way, and it lets you use and control the Mathematica kernel from a .NET program. For Mathematica users, .NET/Link makes all existing and future .NET types an automatic extension to the Mathematica environment. For .NET programmers, .NET/Link turns Mathematica into a scripting shell that lets you experiment with, build, and test .NET types a line at a time. It also makes .NET a powerful environment for writing programs that use the computational services of Mathematica. "