Program.cs中的log4net

Question

I have just set up log4net in my C# WinForms application by adding the reference, adding the configuration to App.config and the load entry in AssemblyInfo.cs. The config is set to catch ALL levels.

In my Program.cs, I am trying to make it catch every single error.

I currently have this:

    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        private static readonly ILog log = LogManager.GetLogger(typeof(Program));
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            try
            {
                log.Info("this works");
                Application.Run(new Forms.Main());
            }
            catch (Exception e)
            {
                log.Info("nothing here", e);
            }
        }
    }

I put the "this works" in just to test that I can actually write to the log file, and this what shows up in the log:

2012-09-30 23:00:53,959 [INFO ] - this works

My log4net is also set up to write to the Immediate Window, so I've created some errors on purpose and this is what I see in the window:

ContractManagement.Program: 2012-09-30 23:08:09,177 [INFO ] - this works
A first chance exception of type 'System.Data.SqlServerCe.SqlCeException' occurred in System.Data.SqlServerCe.dll

I would have expected to see the second error in the logs as well, but there is no sign of it :(

---

Following Keith Nicholas's comment, I have done this:

static void Main()
{
    Application.EnableVisualStyles();
    Application.SetCompatibleTextRenderingDefault(false);

    log.Info("this works");
    throw new System.ArgumentException("Keith Nicholas Test");
    //Application.Run(new Forms.Main());

}

And the log file shows:

2012-09-30 23:19:12,090 [INFO ] - this works
System.ArgumentException: Keith Nicholas Test
   at ContractManagement.Program.Main() in c:\ContractManagement\ContractManagement\Program.cs:line 25

Answer 1

A first chance exception of type 'System.Data.SqlServerCe.SqlCeException' occurred in System.Data.SqlServerCe.dll

It's not a problem with your log4net configuration. One of the internal libraries threw an exception and then caught it so it never made it to your catch clause. The development environment wrote out the the information about the caught exception directly to the immediate window.

Yes log4net is writing to the immediate window, but not everything in the immediate window is from log4net.

[update - to reflect more general issues with logging multiple threads]

Although not directly related to your question, sometimes a class which has been instrumented with log4net logging, can be executing in different threads at the same time. You may get debug, info and/or error methods from multiple threads at the same time. Recommend you update the message pattern in your App.config to include the thread, so you can keep track of which message came from which thread. For example:

<conversionPattern value="%level %thread %logger - %message%newline" />

This is just an example - you did not include your conversion pattern so I'm not sure exactly what yours would look like if you were to add %thread.

Answer 2

If an exception is thrown from a new thread, it won't get caught by that catch block....

Just to prove your logging is working ok :-

instead of running your application, just throw a new Exception right after the first log.Info to prove your exception logging works.

like :-

try
{
    log.Info("this works");
    throw new System.ArgumentException("Keith Nicholas Test");
}
catch (Exception e)
{
   log.Info("nothing here", e);
}

Answer 3

Lots of Googling later, I have:

static class Program
{
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    private static readonly ILog log = LogManager.GetLogger(typeof(Program));
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);

        AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException);
        Application.ThreadException += new System.Threading.ThreadExceptionEventHandler(Application_ThreadException);
        AppDomain.CurrentDomain.FirstChanceException += FirstChanceHandler;

        Application.Run(new Forms.Main());
    }

    private static void Application_ThreadException(object sender, ThreadExceptionEventArgs e)
    {
        log.Info(e.Exception.Message);
    }

    private static void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
    {
        log.Info(e);
    }

    static void FirstChanceHandler(object source, FirstChanceExceptionEventArgs e)
    {
        log.Info(e.Exception.Message);
    }
}

This catches the FirstChanceExceptions I was hoping to capture:

2012-10-01 00:24:02,532 9 ContractManagement.Program [INFO ] - The database file cannot be found. Check the path to the database. [ Data Source = C:\ContractManagement\ContractManagement\bin\Debug\ContractManagement.sdf ]