How to specify the path to a VS extension DLL from an MSBuild <UsingTask> tag - msbuild

Question

I'm developing a Visual Studio extension. The extension's associated VS project template includes a call to a custom task in the extension's DLL:
<UsingTask TaskName="MyTask" AssemblyFile="path to MyDLL.dll" />
The extension will be installed in the usual place, through use of the VSIX installer.
My question is: Is there a good MSBuild property or macro that I can use to construct the path to the extension's DLL (i.e., MyDLL.dll)? I'm aware of $(DevEnvDir) and could extend that path when using the project and extension in Visual Studio 2015 (append \VendorName\ProductName\Version), but that doesn't seem to work in VS 2017, where the appended path uses a mangled name that can't be predicted ahead of time (or can it?). There's also the issue that the project/extension should work in the VS experimental instance, which does not appear to reflect $(DevEnvDir).
Is there any good way to do this with MSBuild properties, or will I need to look at alternatives like environment variables or the registry?

Answer 1

Is there any good way to do this with MSBuild properties, or will I need to look at alternatives like environment variables or the registry?
You can use environment variables or the registry to achieve it.
environment variables
you could use environment variables like this:
<UsingTask TaskName="MyTask" AssemblyFile="$(yourenvironmentvariablesname)MyDLL.dll" />
For more information, please refer to:
https://learn.microsoft.com/en-us/visualstudio/msbuild/how-to-use-environment-variables-in-a-build
registry
You could use registry like this:
<UsingTask TaskName="MyTask" AssemblyFile="$(Registry:HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework#DbgManagedDebugger)MyDLL.dll" />
Note: please change related registry path as you want.
https://blogs.msdn.microsoft.com/msbuild/2007/05/04/new-registry-syntax-in-msbuild-v3-5/

Answer 2

The solution that made sense for me was to create a wizard and to set the path to the extension install location in the replacements dictionary and use the replacement in the template with the UsingTask.
public class ProjectLocationWizard : IWizard
{
public void BeforeOpeningFile(ProjectItem projectItem)
{
}
public void ProjectFinishedGenerating(Project project)
{
}
public void ProjectItemFinishedGenerating(ProjectItem projectItem)
{
}
public void RunFinished()
{
}
public void RunStarted(object automationObject, Dictionary<string, string> replacementsDictionary, WizardRunKind runKind, object[] customParams)
{
var wizardDirectory = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
replacementsDictionary.Add("$installlocation$", wizardDirectory);
}
public bool ShouldAddProjectItem(string filePath)
{
return true;
}
}
<UsingTask AssemblyFile="$installlocation$\MyTask.dll" TaskName="MyTask" />
Although the wizard docs say to sign the wizard assembly, I did not, and it works fine without.