C# - How to Create Trial Version Windows Application

Make your application with trail version using Registry Key in C#

In previous articles I explained about ASP.Net - Encrypt and Decrypt Password, How to encrypt decrypt connection string in webconfig file?

If customers can use your app for free during a trial period you can design your app to exclude or limit some features during the trial period. In this article I will explain how to create a trail version windows applications, Make Your Application with Trial Version or C# window app a 30 day trail.

The best way to make windows application as trail software, is by setting the key in the registry. You can save a key in registry and in your application you can validate and check the validity of application. Find the source code below:

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.Security.Cryptography;

namespace CreateTrailWinApp

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        private void Form1_Load(object sender, EventArgs e)

        {

            try

            {

                CreateTrailfunctionality();

            }

            catch (Exception ex)

            {

                MessageBox.Show(ex.Message);

            }

        }

        private void CreateTrailfunctionality()

        {

            try

            {

                Microsoft.Win32.RegistryKey EncryptedKey;

                RSACryptoServiceProvider crypto = new RSACryptoServiceProvider();

                EncryptedKey = Microsoft.Win32.Registry.CurrentUser.CreateSubKey(@"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\EncryptedDate");

                object value = EncryptedKey.GetValue("EncryptedDate");

                if (value == null)

                {

                    EncryptedKey = Microsoft.Win32.Registry.CurrentUser.CreateSubKey(@"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\EncryptedDate");

                    string keyvalue = DateTime.Now.ToString("dd-MMM-yyyy");

                    byte[] messageBytes = Encoding.Unicode.GetBytes(keyvalue);

                    string encryptedMessage = Convert.ToBase64String(messageBytes);

                    EncryptedKey.SetValue("EncryptedDate", encryptedMessage);

                }

                else

                {

                    byte[] encryptedMessage1 = Convert.FromBase64String(value.ToString());

                    string key = System.Text.Encoding.Unicode.GetString(encryptedMessage1);

                    DateTime date = Convert.ToDateTime(key);

                    MessageBox.Show(date.ToString("dd-MMM-yyyy"));

                }

            }

            catch (Exception e)

            { }

        }

    }

}

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