How to get Extension Methods to display when using assembly references

[UmaHarano]

I am having issues with extension methods to be listed in the base class.
I have two csproj files in my solution:

• Project A with a "Map" class.
• Project B in the same sln has a "MappingExtensions" class that defines extension methods for the Map class that is defined in Project A.

Issue

• If Project B has a "project reference" to Project A:
  Project A's Map class apiPage yml I generate using DocFX lists the extension methods defined in Project B.
• If Project B has a assembly reference to Project A:
  Project A's Map class apiPage yml I generate using DocFX does not list the extension methods defined in Project B. This is the issue.

The problem is my code base only uses "Assembly reference". So I am missing all the extension methods. Is there a solution or work around you can recommend? I cannot use project references.

[UmaHarano]

@yufeih Any ideas on this one? Thanks!