private static object _LogLock = 0;     // needs to be at the containing object's level
                                        // so, in this case, static object global

// Convenience function to log jive.
public static void logStuff(string strToLog)
{
        // obviously C:\temp must exist
        string strLogFile = "C:\\temp\\appLog.log";
        string strDateFormat = "MM/dd/yyyy hh:mm:ss.fff tt";

        try
        {
                // When you have multiple AJAX (because, duh, asynchronous)
                // calls going at once which, each of which might be calling
                // parts of your .NET website that log stuff, you're likely to
                // eventually run into concurrent logStuff calls.  And since
                // one "logStuff" might have your log file locked when the
                // second comes along and also wants to log some stuff, you're
                // going to want to lock the process so that you don't throw
                // exceptions.  Now, the second logStuff call will wait
                // patiently until the lock on _LogLock is released.

                // More information here:
                // http://stackoverflow.com/questions/7419172/streamwriter-lock-not-working
                // http://msdn.microsoft.com/en-us/library/c5kehkcz(v=vs.71).aspx
                lock (_LogLock)
                {
                        if (!File.Exists(strLogFile))
                        {
                                // Create a file to write to.
                                using (StreamWriter sw = File.CreateText(strLogFile))
                                {
                                        sw.WriteLine("Our application's log file.");
                                        sw.WriteLine("Created " 
                                                + DateTime.Now.ToString(strDateFormat));
                                        sw.Close();
                                }
                        }

                        // This text is always added, making the file longer over time
                        // if it is not deleted or cleaned up.
                        using (StreamWriter sw = File.AppendText(strLogFile))
                        {
                                sw.WriteLine(DateTime.Now.ToString(strDateFormat) + ":");
                                sw.WriteLine("\t" + strToLog.Replace("\n", "\n\t"));
                                sw.Close();
                        }
                }
        }
        catch (Exception e)
        {
                // probably b/c C:\temp\ doesn't exist or isn't accessible.
                System.Diagnostics.Debugger.Break();    

                // insure that's the problem.
                // In production, if you forget to remove this exception handler
                // or to move log location to something valid on the server/box, 
                // it'll quietly fail.
        }

}

Labels: c#, code, noteToSelf