Reflection between projects based on attributes

I have 2 projects, project A and Project B.

In project A, I have a class ClsPersoon that is decorated with the attribute Myperson.

In project B I use reflection on the exe file from project A and i want to select al types that have customAttribute MyPerson but I get an error on getCustomAttributes because this attribute is not known in project B.

How to solve this without a reference between both projects?