How can I create a Product Key for my C# App

How can I create a Product Key for my C# Application?

I need to create a product(or license( key that I update annually.  Additionally I need to create one for trial versions.

Thanks,

Jeremy
How can I create a Product Key for my C# App
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How can I create a Product Key for my C# Application?

I need to create a product(or license( key that I update annually.  Additionally I need to create one for trial versions.

Thanks,

Jeremy