Can I use manifests to specify an optional dependency on a COM server?

Question

I'd like to use manifests to specify a dependency on a COM server (reg-free COM).

The consumer application will mostly work fine without the COM server - only something like 1,7% of its functionality uses the COM server. So with plain old regsvr32 it would start and work fine until the user would do something that would trigger CoCreateInstance() call and at that point the consumer would get an error message.

Now I've played with manifests for a while and it looks like the consumer wouldn't even start unless the COM server assembly it depends on is present in the file system. That's no good.

I added the "addiditional manifest" with the following content:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
   <dependency>
       <dependentAssembly>
           <assemblyIdentity
              type="win32"
              name="TheComServer.X"
              version="1.0.0.0"/>
       </dependentAssembly>
   </dependency>
</assembly>

Is there a way to use reg-free COM with manifests and make the dependency optional - so that the consumer program starts and works fine until CoCreateInstance() is actually called?

Answer 1

You are going to have to provide at least the manifest for the reg-free COM assemblies.

The application manifest references the assemblies the application wants - the component manifests are processes at application startup - and specify the com objects the assembly exports.

They have to be specified as the activation context is loaded.

You can use the activation context API to manually create an activation context and load assemblies into it - and then ensure that that context is current when you try to CoCreateInstance.