Interactive Brokers provides a great API for programmatic trading, but they do not offer a native C# version. I have ported their java socket interface to C#, and am maintaining it as IB introduces new features. I have also incorporated inline documentation into the library for reference purposes.

Source Code
Readonly subversion access is provided to http://svn.karlschulze.com:8080/svn/ibapi/. Use the username “svnreadonly” and the password “Re@dOnly23″.

Old Versions

View the Blog post here, and the 9.20 post here.