How to connect a library from an older (2.0) framework to an application using a newer (4.0) framework?

Question

.NET

Says "could not be found (are you missing a using directive or an assembly reference?)"

Answer 1

(I'll try to write the actions in more detail)
I use the dll compiled under the 2nd framework in the project on the 4th framework. To connect it, I add it to the project for convenience, in order to immediately see where it lies from the solution,
and then in the window for adding a link I look for it in the project folder where it was created, via browse.
Good luck!

Answer 2

Strange, in theory, should see.
Try to set the version of the environment in app.config, nothing else comes to mind.

<?xml version="1.0"?>
<configuration>
  <startup useLegacyV2RuntimeActivationPolicy="true">
    <supportedRuntime version="v4.0"/>
  </startup>
</configuration>

Answer 3

regsvr32 did on DLL'ku?