Question

I’m working on an application which shows a random movie quote once in a minute, but I can’t get the code to work.

I’m using a UserControl which contains of a label to show the quote, and in it’s Page_Load I want to instantiate “Quote”. The constructor starts a timer which calls the function that’s randomize a quote once in a minute, and returns it to the Page_Load and shows it in the Label.Text.

The line with the timer gives me the following error message: ‘System.Timers.Timer’ does not contain a constructor that takes 4 arguments’, which for me makes no sense?

public class Quote {
    List<string> movieQuote;

    private string RandomQuote(object state) {

        movieQuote.Add("quote1");
        movieQuote.Add("quote2");
        movieQuote.Add("quote3");
        movieQuote.Add("quote");

        Random randNr = new Random();
        int aRandomPos = randNr.Next(1, movieQuote.Count);

        string quote = movieQuote[aRandomPos];

        return quote;
    }

    public Quote() {
         movieQuote = new List<string>();
         Timer timer = new Timer(RandomQuote, null, TimeSpan.Zero, TimeSpan.FromMinutes(1));
    }
}

Answer 1

First off, you need to understand that there are a few different Timer classes built into .NET, with slightly different behaviors based on the most likely requirements of users of a timer from a particular library. System.Timers.Timer truly doesn’t have a constructor with four arguments. What you probably wanted was a System.Threading.Timer.

Also, I should tell you that Timers in a web environment are just bad. Bad, bad, bad. The reason why is because of the ASP.NET lifecycle. The short of it is that an instance of your codebehind class only exists in memory for as long as it takes to render the HTML page. After that, it’s released and GCed. When a new request comes in, for a form event or whatever, a new instance of the class is created. The upshot is that a Timer created during Page_Load will go out of scope and be disposed of long before it fires the Tick event.

Instead, what you want is an AJAX-y area of your page which uses a Javascript Timeout to trigger a call to the server which will generate a new random quote. That will be returned in XML format to the client which can write it into the DOM of the page, without a full postback. There are AJAX interop controls you can add to your page to streamline this (it will trigger a full postback, but only actually redraw the area bounded by an AJAX UpdatePanel), or you can give your page a simple SOAP or JSON service call that will return the string without any other server-side logic having to run.