limited trial period in C #

Question

hi, I want to use C # to do a program, enabling prompt trial period, after a trial period prompted to register. thank.

Vulpes · Answer

Here's a very simple way of creating a time-limited application. The first time the application is run this creates and stores the expiry date in a file and, then checks the expiry date against the current date each subsequent time the application is run. However, you can't just store this file in (say) the application folder because, if you did, the user could simply delete it and restart the trial period. You need to bury it in the file system so that it will be difficult for an ordinary user to find it and the following approach uses 'isolated storage' to achieve that aim: using System; using System.IO; using System.IO.IsolatedStorage; static class Program { static void Main(string[] args) { int period = 30; // trial period using (IsolatedStorageFile isf = IsolatedStorageFile.GetMachineStoreForAssembly()) { if(!isf.FileExists("expiry.txt")) { using(var iss = new IsolatedStorageFileStream("expiry.txt", FileMode.Create, isf)) { using (var sw = new StreamWriter(iss)) { string s = DateTime.Today.AddDays(period).ToString(); sw.WriteLine(s); } } } else { using(var iss = new IsolatedStorageFileStream("expiry.txt", FileMode.Open, isf)) { using (var sr = new StreamReader(iss)) { string s = sr.ReadToEnd(); DateTime expiry = DateTime.Parse(s); if (DateTime.Today > expiry) { Console.WriteLine("Your free trial has expired. Please register to continue using the application"); return; } } } } } // code for rest of application Console.WriteLine("Rest of application continuing ..."); Console.ReadKey(); } } It will be more secure if you give your assembly a strong name and store it in the GAC. Otherwise, it will be identified by its file path and the user will then be able to defeat the trial period by either renaming or copying it to a different location which will cause the isolated storage to be reset. However, all limited trial applications which depend on the system clock can be defeated by the user temporarily changing the system date. You can prevent this by obtaining the date from the internet, using a web service or otherwise, but this obviously requires that the user has an internet connection which can cause a number of problems in itself. A better idea IMO is to restrict the number of times the application can be run without any time restriction. You can then simply update the count in the file on each running.

Vulpes · Answer

The FileExists() method was introduced in .NET 4.0 (VS 2010) so I deduce that you must be using an earlier version. To check whether the isolated storage file already exists, try replacing this line: if(!isf.FileExists("expiry.txt")) with this: if(isf.GetFileNames("expiry.txt").Length == 0)

Sanjeeb Lenka · Answer

hi, refer to this link http://www.c-sharpcorner.com/uploadfile/tanmayit08/make-your-application-with-trial-version/ http://www.codeproject.com/Articles/15496/Application-Trial-Maker

Jignesh Trivedi · Answer

hi, Please refer our Recommended solution. it might help you. http://www.c-sharpcorner.com/uploadfile/tanmayit08/make-combination-of-keys-for-our-trial-version-application/ http://msdn.microsoft.com/en-us/library/windows/apps/hh694065.aspx

Vengat Yadve · Answer

Hi please tell me how to set date manually...

Ken H · Answer

Well,Files that are created through the IsolatedStorageFile if it has physical path, I will try to find its folder directory, but it can't be found. thanks.

Ken H · Answer

hi Vulpes, if (!isf. FileExists ("expiry.txt")) //System.IO.IsolatedStorage.IsolatedStorageFile not include "FileExists" define

Nitesh Luharuka · Answer

Very Good one Vulpes!!!

Ken H · Answer

hi, I just need a simple example Oh. For example, I wanted to be valid for 30 days to write to a binary file, every time you start the program determines whether the current date is greater than 30 days, if more than 30 days then it prompts the user and exit. :) thank.

limited trial period in C #

Answers (9)