As I noted in an earlier post :
Source Code for a Working Implementation of ITextTemplatingEngineHost, I am trying to build a custom host for T4. The answer to my query about available source code for a working custom host lead to the code in the MSDN documentation. That code worked. Using that code as a baseline, I was able to isolate the cause of my problem.
My situation is that I want to expose the custom host in the template file. Following the example in MSDN, I wrote the following code for the ProvideTemplatingAppDomain:
public AppDomain ProvideTemplatingAppDomain(string content)
{
// This host will provide a new application domain each time the
// engine processes a text template.
// -------------------------------------------------------------
return AppDomain.CreateDomain("Generation App Domain");
}
This works fine if I supply a new AppDomain but do not include the "hostspecific=true" parameter on the template directive. It also works just fine if I supply the current Appdomain and include the "hostspecific=true" parameter. It DOES NOT WORK if I supply a new AppDomain and also include the "hostspecific=true" parameter. The issue is that the Engine class is not serializable. Apparently, it must be serializable to move across the AppDomain boundary.
I have to specify the "hostspecific=true" parameter to make the functionality that I am trying to provide work. In the short term, I can work around this by re-using the AppDomain, but I wonder how that will affect Visual Studio performance. Am I right in thinking that the custom tool will run in a separate process space? If it does, the AppDomains will only live for the duration of the code generation process; there would be no accumulation in memory. But the author of the MSDN sample took some effort to mention that creating a searpate AppDomain was a good idea. Is there a way to get a new AppDomain and "host specific" at the same time?
Jon Stonecash
How to handle Serialization Issue with a Custom Host Implementing ITextTemplatingEngineHost
