The following can get you started on getting process information...
How to get information about process in C#? - Stack Overflow[
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You're not clear on how you'll start and manage your application. If you want an application that appears in the notification area, but does not normally have a form, the following might help:
Formless Notify Icon Application[
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If instead, you prefer it to run as a Windows service, check out the following:
Walkthrough: Creating a Windows Service Application in the Component Designer | Microsoft Docs[
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Depending on your system, its likely you'll have to run with elevated privileges to monitor a different process.