I was able to play with BizTalk 2009 Beta on Dev 10 a little more and had some advice. When I installed earlier, I had not seen that the Developer Tools and SDK was grayed out and this was the reason the .btproj extension had not been installed properly. I eventually realized that on the VS 2010 CTP VPC, VS 2008 BIDS did not have VS 2008 SP1 so this was required to get the BizTalk 2009 Beta VS extensions to install at all.
With the VS extensions for BizTalk installed correctly, I was still not able to open BizTalk 2009 projects using VS 2010. For some reason the VS extensions are just not being applied to VS 2010.
Here is my updated install order to get BizTalk to work with as much as possible:
Team explorer for VS 2008 did connect fine to the TFS 2010 server though.So I still wanted to answer a few questions. I was able to add a BizTalk 2009 project to TFS 2010 through VS 2008 w/ Team Explorer 2008 and view the source code in VS 2010, I was just not able to open the BizTalk projects. Here is a screenshot from VS 2010 with the BizTalk files in source control in TFS 2010:
So this is good because it means it is possible to upgrade to TFS 2010 without affecting BizTalk solutions. VS 2008 will just need to remain in order to keep editing BizTalk 2009 projects.
The other question I had was whether a BizTalk 2009 project can reference a .NET 4.0 assembly. VS 2008 SP1 cannot create .NET 4.0 versioned projects, so the reference would have to be a GAC or file reference rather than a project reference. I created a .NET 4.0 assembly from VS 2010 and referenced some v4.0.11 assemblies and recompiled. Then I tried referencing the assembly in my BizTalk project in VS 2008. It looks like it is possible to reference a .NET 4 assembly from VS 2008 for a BizTalk project but I was unable to build it successfully. Here is the message I got when adding the reference:
After trying to compile I realized it was not possible to reference a .NET 4 assembly from Visual Studio 2008 SP1 (yet). I also tried referencing an M project using the latest Oslo January CTP SDK and was not able to successfully.
So the good news is that you can migrate your TFS investment ahead of BizTalk and the BizTalk files will still check-in and import successfully. My next task will be to see how well the new ALM features of BizTalk 2009 translate over to working on TFS 2010.