使抛出异常起作用

Question

I've been trying to write a small program with these instructions:

In this assignment you should write a simple web application with one link on the front page of the web. If the link is clicked, the user will simply be routed to the front page again (using RedirectToAction ). However, occasionally, the action method might throw an exception (but not always). Occasionally (one in every 5 occasions) the method should throw an ArgumentException , and occasionally (again, in maybe 1 in a 5), it should throw a custom Exception object you should declare yourself, called MyApplicationException.

In HomeController I have:

public class HomeController : Controller
{
    List<Logger> m_loggers = new List<Logger>();

    protected override void OnException(ExceptionContext fc)
    {
        base.OnException(fc);
        Exception ex = fc.Exception;

        Logger.Instance.Log(ex);
    }

    public ActionResult Index()
    {
        string strLogFile = System.Configuration.ConfigurationManager.AppSettings["LogFile"];
        string strEmail = System.Configuration.ConfigurationManager.AppSettings["Email"];

        try
        {
            RedirectToAction("Index");

            using(MailMessage message = new MailMessage())
            {
                message.To.Add(strEmail);
                message.Subject = "Villuskilaboð";
                message.Body = "Upp hefur komið villa frá Skilaverkefni 4!";

                using(SmtpClient client = new SmtpClient())
                {
                    client.EnableSsl = true;
                    client.Send(message);
                }
            }
        }
        catch(Exception ex)
        {
            Random r = new Random();
            int rand = r.Next(1000);

            if(rand % 5 == 0)
            {
                throw new System.ArgumentException("Randon villuskilaboð handa þér!");
            }

            Debug.WriteLine(ex.Message +
                            Environment.NewLine +
                            ex.StackTrace);
        }

        return View();
    }

Logger class:

public class Logger
{
    List<LogMedia>m_loggers = new List<LogMedia>();

    private static Logger theInstance = null;

    public static Logger Instance
    {
        get
        {
            if (theInstance == null)
            {
                theInstance = new Logger();
            }
            return theInstance;
        }
    }

    private Logger()
    {
        m_loggers = new List<LogMedia>();
        //m_loggers.Add(new TextFileLogMedia { });
        //m_loggers.Add(new EmailLogMedia { });
    }

   public void Log(Exception ex)
   {
       foreach(LogMedia log in m_loggers)
       {
           log.LogMessage(ex.Message + Environment.NewLine);
       }
    }
}

LogMedia

public class LogMedia
{
    public virtual void LogMessage(string Message)
    {
    }

    public class OutputWindowLogMedia: LogMedia
    {
        public override void LogMessage(string Message)
        {
            System.Diagnostics.Debug.WriteLine(Message);
        }
    }

    public class TextFileLogMedia: LogMedia
    {
        public override void LogMessage(string Message)
        {
            //File.AppendAllText("c:\\Temp.Log.txt", Message);
        }
    }

    public class EmailLogMedia: LogMedia
    {
        public override void LogMessage(string Message)
        {
        }
    }
}

I´m stuck for now and seems not getting it to work, my Visual Studio crash and I get error up, don't think that is the exception, I´m so new to it so maybe it´s the box that should come up :) But the email never get to my account.

What am I still missing to make everything work? I know the file-thing isn't in this code, trying to make the other things to work first.

I've added information about my eMail in web.config .

Answer 1

You really need to rework your Index() method. I'm not in front of my computer with Visual Studio, but I'm surprised you code gets past the first line in your try . Having the RedirectToAction("Index") should throw a warning that the rest of the method will never be reached, and create an infinite loop when you try to access the method. The RedirectToAction("Index")` you have in your code does nothing as you don't return the results of that. Thank you Erik Noren

This would be how I'd structure your method instead:

public ActionResult Index() {
    // No need to go higher, as it's always just as random with a modulo
    int rnd = (new Random()).Next(5); 

    try {
        switch (rnd) {
            case 1: // Or any of the 5 numbers you want.
                throw new ArgumentException();
            case 4: // Again, any of the 5 numbers
                throw new MyApplicationException();
            default:
                return RedirectToAction("Index");
        }
    }
    catch (Exception ex) {
        // Do your error logging here.
    }
}