How to detect when client delete license file desktop app ?

Question

I working on desktop application windows desktop made by csharp

I make license file have period of license as 30 day and start date and computer mac address

my issue is clients delete license file so desktop app start as first day after delete this file

so how to prevent users from delete license file

or with another way how to make my app detect that file created before and deleted so can't open my app

Answer 1

This question has been asked millions of times and my recommendation is to use a paid service.

If you want to go cheap then write the required file under AppData\Local in a folder you create. The average customer will not find this folder e.g.

var licenseFile = 
    Path.Combine(Environment.GetFolderPath(
        Environment.SpecialFolder.LocalApplicationData), "Secret", "license.dat");