OK, I figured it out. The problem was that apparently since the last release of the T4MVC package, Microsoft changed the location of the ITextTemplateHost interface, so I needed to import another namespace. Also, the .dll files with these namespaces aren t imported in the default ASP.NET MVC template project. This is what I did to make it work:

1. Add references to the following .dll files (search paths on my machine in brackets):

   • Microsoft.VisualStudio.TextTemplating.10.0.dll (C:WindowsMicrosoft.NETassemblyGAC_MSILMicrosoft.VisualStudio.TextTemplating.10.0v4.0_10.0.0.0__b03f5f7f11d50a3aMicrosoft.VisualStudio.10.0.dll)

   • Microsoft.VisualStudio.TextTemplating.Interfaces.10.0.dll (C:WindowsMicrosoft.NETassemblyGAC_MSILMicrosoft.VisualStudio.TextTemplating.Interfaces.10.0v4.0_10.0.0.0__b03f5f7f11d50a3aMicrosoft.VisualStudio.TextTemplating.Interfaces.10.0.dll)

2. Make sure the following namespaces are both imported in T4MVC.tt (just follow the syntax that s already in the file).

   • Microsoft.VisualStudio.TextTemplating

   • Microsoft.VisualStudio.TextTemplating.Interfaces

3. Delete all generated code files (they ll appear if you expand the T4MVC.tt in Solution Explorer).

4. Build project. If no files are generated, open T4MVC.tt, edit something, don t save and build. That should do it!

ADDENDUM - ASP.NET MVC 3 RTM

As an addendum to this issue, if you have just installed ASP.NET MVC 3 RTM, you may hit similar problems in projects that were created using one of the MVC 3 Release Candidates.

To solve:

Make sure that you have T4MVC.2.6.40 or later installed using NuGet.

Ie, reinstall T4MVC using Tools >> Library Package Manage. In the Console, type:

uninstall-package t4mvc 

and then:

install-package t4mvc 

to get the latest version.

You will now probably get the following error in the T4MVC.tt file:

A namespace cannot directly contain members such as fields or methods

Open the file, make it dirty (eg, by deleting the comment with the squiggly line) then close WITHOUT SAVING!!! See David Ebbo s answer, t4mvc.tt NEEDS to be dirty!

Recompile and go get a life.

Seems you got it working, but let me add a few points here.

About the need to import Microsoft.VisualStudio.TextTemplating.Interfaces, I added a comment about that at the top of T4MVC.tt. But yeah, it s easy to miss.

Now for the confusing part: while those interfaces indeed moved to that different namespace in Beta2, the T4 team had a change of heart and decided to move them back again to the original namespace to avoid confusion. So when the next RC build comes out, this namespace will be gone.

About the need to import DLLs, I m surprised that you need this, as it works for me without it.

Final note: in step #4, it should be harmless if you save here. What happens is that T4MVC has logic that keeps itself dirty, so even if you save, you ll see it marked as unsaved (this can be turned off in the settings file).

Hope this helps!