我如何“约会”保护我的申请？

Question

I've built a little WindowsForm app from a standard beginner's tutorial. The kind where you use controls like buttons and textboxes to add 2 numbers and have the result show up in a textbox.

Anyways, I want to make it so that when a user clicks on my .exe, it checks against my built-in expiration date before even launching the program/window. That is, if my expiration date were today Oct. 30, nothing happens, no window form even shows up. However, if my expiration date were to be Oct. 31, everything proceeds normally and windows and forms show up. But, tomorrow on Oct. 31 (expiration date) and any day after tomorrow if the user were to run my .exe, nothing would happen.

I think my code would look something like this:

DateTime expiration = new DateTime(2013, 10, 31) //Oct. 31, 2013
If (DateTime.Today < expiration) //proceed normally
else // do nothing, nothing happens for the user

From the tutorial, most of my understanding is confined to code written inside the public Form1 : Form part of the code:

namespace WindowsFormsApplication4
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
    }
}

Where would I insert code to check today's date against my expiration date so that no forms are loaded?

Answer 1

Look at Program.cs in your Solution Explorer. You can add this code inside the Main function, and call Application.Exit() to leave the application if the condition you have specified hasn't been met.

Answer 2

I won't recommend using "Local Time" for this because user can take the freedom of changing it anytime.

Probably you'll have to get current time from some "Time server"

private static readonly DateTime expiration = new DateTime(2013, 10, 31);
static void Main()
{
    DateTime currentTime = GetTimeFromSomeTimeServer();//Implement yourself
    if (currentTime.Date >= expiration.Date)
    {
        return;//Dont run the app
    }
    //Rest of your code...
}

Answer 3

You most likely want this in the Program.cs file, here's a simple example

static class Program
{
    static DateTime expiration = new DateTime(2013, 10, 31);

    /// <summary>
    /// The main entry point for the application
    /// </summary>
    [STAThread]
    static void Main()
    {
        if (DateTime.Today < expiration.Date) 
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
        else
        {
            Application.Exit();
        }
    }
}

However, just bare in mind that this isn't really the recommended approach for enforcing an expirable application (eg trial software). Generally it's better to use some form of robust licensing system, hard-coding the date into the exe is by no means full-proof and easily exploitable.