Logging Unhandled Exceptions

Bugs are sometimes unavoidable. They’re best caught during the development or testing phase. There might be some cases where the developer forgot to handle possible exceptions in a function. It could be possible that this exception isn’t handled anywhere at all. But even so, it is still possible to catch this exception. To do this we handle the UnhandledException event of the current AppDomain. We should do this in our static void Main() before calling Application.Run([Main Form])

Here’s a small snippet to accomplish this task.

[C# CODE]

static void Main()
{
  AppDomain.CurrentDomain.UnhandledException +=
    new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException);
  Application.Run(new MainForm());
}

static void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
{
  Exception exception = (Exception)e.ExceptionObject;
  if (exception != null) {
    Error.Append(exception.Message, exception.StackTrace);
  }
}

Now we need a mechanism for saving to a Error log file. Let’s create a simple class called Error() and add a function called Append(string message, string stacktrace)

[C# CODE]

public class Error
{
  internal static void Append(string message, string stacktrace)
  {
    string file = string.Format(“{0}\Errors.txt”,
      Path.GetDirectoryName(Assembly.GetExecutingAssembly().GetName().CodeBase));
    if (File.Exists(file)) {
      FileInfo fi = new FileInfo(file);
      if (fi.Length > 100 * 1024) {
        fi.Delete();
      }
    }
    StreamWriter sw = new StreamWriter(file, true, Encoding.UTF8);
    sw.WriteLine(string.Format(
      “-=-=-=-=-=–=-=-n{0}nMESSAGE:n{1}nSTACK TRACE:n{3}n”,
        DateTime.Now, message, stacktrace));
    sw.Close();
    }
  }
}

The Error() class should be put in a namespace that is accessible throughout the application. This will be very helpful tool for finding those nasty almost impossible to reproduce bugs.

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