<p>My Google-fu is failing me on this question.</p>

<p>I have a coworker who has Visual Studio 2005 on his machine. I have Visual Studio 2008. He wants to open a project I wrote in C# 3.0, and we've gotten that far, but VS2005 barfs on the 3.0 code, like <code>var</code>.</p>

<p>He has the 3.0 and 3.5 frameworks installed, as well as the Visual Studio 2005 Extensions for Windows Workflow. What else does he need? Or are we pursuing a lost cause, a wild goose chase spurred by my thinking that I heard this was possible somewhere one time?</p>

<p>Please don't suggest he install VS2008 or the Express edition. That simply isn't possible at this time. :(</p>

The IDE itself may not support the 3.0 functionality. If you can live without the 3.0 features you can compile to 2.0 which he should be able to run ok.