[c#] C# 30 Days From Todays Date

A bit late to this question, but I created a class with all the handy methods needed to create a fully functional time trial in C#. Rather than your application config, I write the expiry time to the Windows Application Data path, and that will also remain persistent even after the program has closed (it's also tricky to find the path for the average user).

Fully documented and simple to use, I hope someone finds it useful!

public class TimeTrialManager
{
    private long expiryTime=0;
    private string softwareName = "";
    private string userPath="";
    private bool useSeconds = false;

    public TimeTrialManager(string softwareName) {
        this.softwareName = softwareName;
        // Create folder in Windows Application Data folder for persistence:
        userPath = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData).ToString() + "\\" + softwareName + "_prefs\\";
        if (!Directory.Exists(userPath)) Directory.CreateDirectory(Path.GetDirectoryName(userPath));
        userPath += "expiryinfo.txt";
    }

    // Use this method to check if the expiry has already been created. If
    // it has, you don't need to call the setExpiryDate() method ever again.
    public bool expiryHasBeenStored(){
        return File.Exists(userPath);
    }

    // Use this to set expiry as the number of days from the current time.
    // This should be called just once in the program's lifetime for that user.
    public void setExpiryDate(double days)  {
        DateTime time = DateTime.Now.AddDays(days);
        expiryTime = time.ToFileTimeUtc();
        storeExpiry(expiryTime.ToString() );
        useSeconds = false;
    }

    // Like above, but set the number of seconds. This should be just used for testing
    // as no sensible time trial would allow the user seconds to test the trial out:
    public void setExpiryTime(double seconds)   {
        DateTime time = DateTime.Now.AddSeconds(seconds);
        expiryTime = time.ToFileTimeUtc();
        storeExpiry(expiryTime.ToString());
        useSeconds = true;
    }

    // Check for this in a background timer or whenever else you wish to check if the time has run out
    public bool trialHasExpired()   {
        if(!File.Exists(userPath)) return false;
        if (expiryTime == 0)    expiryTime = Convert.ToInt64(File.ReadAllText(userPath));
        if (DateTime.Now.ToFileTimeUtc() >= expiryTime) return true; else return false;
    }

    // This method is optional and isn't required to use the core functionality of the class
    // Perhaps use it to tell the user how long he has left to trial the software
    public string expiryAsHumanReadableString(bool remaining=false) {
        DateTime dt = new DateTime();
        dt = DateTime.FromFileTimeUtc(expiryTime);
        if (remaining == false) return dt.ToShortDateString() + " " + dt.ToLongTimeString();
        else {
            if (useSeconds) return dt.Subtract(DateTime.Now).TotalSeconds.ToString();
            else return (dt.Subtract(DateTime.Now).TotalDays ).ToString();
        }
    }

    // This method is private to the class, so no need to worry about it
    private void storeExpiry(string value)  {
        try { File.WriteAllText(userPath, value); }
        catch (Exception ex) { MessageBox.Show(ex.Message); }
    }

}

Here is a typical usage of the above class. Couldn't be simpler!

TimeTrialManager ttm;
private void Form1_Load(object sender, EventArgs e)
{
    ttm = new TimeTrialManager("TestTime");
    if (!ttm.expiryHasBeenStored()) ttm.setExpiryDate(30); // Expires in 30 days time
}

private void timer1_Tick(object sender, EventArgs e)
{
    if (ttm.trialHasExpired()) { MessageBox.Show("Trial over! :("); Environment.Exit(0); }
}