Authenticating an exectuable object with C # .NET 4.0

We deliver the executable to the client service, which runs this executable in a new process after downloading it from our servers.

The executable is signed (authenticode) with our company's CodeSigning certificate, and now I want to verify that the downloaded executable is actually signed with this CodeSigning certificate to prevent malicious Man-in-the-middle attacks.

But at the moment I can't find any clues on how to test this without using "signtool.exe" (which is not available on the client).

The Download-Service on the client is a .NET 4.0 application written in C #. Therefore, I am looking for a way to verify the authenticity of the uploaded file and only continue if the verification is successful.