I make desktop application using csharp . I face issue I can't protect this desktop application I do it from another client use it. so I ask about way that I can do to prevent another person use it so what I do to protect my app so how to give client 30 day as trial then after that if not pay stop it can you tell me how to do that What I have tried: some developer store data on registry are this best solution for that store on registry or what if user change date time of windows how to handle that can I prevent user from install my app again can any one help me by answer this question by more details if free or source code or library can use it without pay then I prefer that