T4 template adding assembly of existing project in solution

Hi I need to add the assembly of an an existing project in my solution in my T4 Template file. The problem is that my T4 template is in a project called Project.WebApi and the class that I need in my T4 template is inside a project called Project.Common.WebApi.

I have tryed importing the namespace like this:

<#@ import namespace="Project.Common.WebApi.T4TemplateAttribute" #>

But I get this error:

The type or namespace name 'Project' could not be found (are you missing a using directive or an assembly reference?)

I have tryed adding the assembly like this:

<#@ assembly name="Project.Common.WebApi" #>

And I got this error:

Compiling transformation: Metadata file 'Project.Common.WebApi' could not be found

My project that contains the T4Template (Project.WebApi) has a reference to the Project.Common.WebApi but from what I read T4Template does not use the references in the projects.

How can I solve this issues?

T4 works nearly completely independent from the rest of your code. You're on the right track though, with the assembly directive, but you'll need to specify a full path to the actual DLL of the assembly, unless the assembly is in the GAC (which it probably isn't).

Luckily, however, you can use MSBuild macros in T4 directives. So, you'll probably get something like

<#@ assembly name="$(SolutionDir)Project.Common.WebApi\bin\Debug\Project.Common.WebApi.dll" #>

See MSDN for some more background on this syntax.

You still also need the import namespace directive.

Finally, be wary of project build order. The project that contains your T4 template now depends on Project.Common.WebApi, so you'll need to make sure that Project.Common.WebApi is built first. Otherwise, your T4 template might accidentally link to an older version of the assembly, making bugs really hard to track.

If you already have a project reference to it, you're all done, but otherwise you need to set up the dependencies correctly. You can do this in Visual Studio via the "Project Dependencies..." dialog. Right-click the project to find it.

In case your project with T4 template has direct reference to the project, you can use $(TargetDir)

<#@ assembly name="$(TargetDir)Project.Common.WebApi.dll" #>

<#@ assembly name="$(TargetPath)" #>

As simple as that.