Centralised Exception Handling in C# Windows Application

 

Introduction

You might have been come across a situation when you may need yourapplication to Log all your application errors. This can be done using try catch blocks.But what about unhandled exceptions. When your application comes acrossan unhandled exception, your application will exit just showing anerror window. This may sometimes result in loss of data. To avoid this,you need to handle all the unhandled exceptions from a centralizedmethod. This article explains a simple way of centralized exceptionhandling.

Using the Code

There are two sources where the exceptions are raised. Either theexception can be raised in the main thread or it can be raised in theadditional threads used in the application. Let us now walk in to thecode how to handle this.

static class Program
{
    [STAThread]
    static void Main()
    {
        // Add handler to handle the exception raised by main threads
        Application.ThreadException += 
        new System.Threading.ThreadExceptionEventHandler(Application_ThreadException);
        
        // Add handler to handle the exception raised by additional threads
        AppDomain.CurrentDomain.UnhandledException += 
        new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException);
        
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new Form1());
        
        // Stop the application and all the threads in suspended state.
        Environment.Exit(-1);            
    }
    
    static void Application_ThreadException
    (object sender, System.Threading.ThreadExceptionEventArgs e)
    {// All exceptions thrown by the main thread are handled over this method
        
        ShowExceptionDetails(e.Exception);
    }
    
    static void CurrentDomain_UnhandledException
    (object sender, UnhandledExceptionEventArgs e)
    {// All exceptions thrown by additional threads are handled in this method
        
        ShowExceptionDetails(e.ExceptionObject as Exception);
        
        // Suspend the current thread for now to stop the exception from throwing.
        Thread.CurrentThread.Suspend();
    }
    
    static void ShowExceptionDetails(Exception Ex)
    {
        // Do logging of exception details
        MessageBox.Show(Ex.Message, Ex.TargetSite.ToString(), 
        MessageBoxButtons.OK, MessageBoxIcon.Error);
    }
}

In the above class, we shall attach an event handler to two events. It is better to attach these events as soon as the main method starts.

Application.ThreadException - This event will be raised when an exception is thrown in the main thread. If we add an event handler, then the exception is handled over the method.

AppDomain.CurrentDomain.UnhandledException - This eventwill be raised when an exception is thrown in the additional threadsused in the application. The worse scenario here is as soon as thehandlers' execution gets over, the exception is again thrown whereasthe application ends. This need to be handled. Here I have used a bitof code to handle this situation and continue the execution of theapplication without interruption.

The logic I have used to overcome this situation is just suspendingthe thread in the event handler, so that the application continues towork fine. Again a problem arises in suspending this thread. When themain form is closed, the application normally needs to exit, but as thethread is in suspended state, the application will still remainrunning. So to exit the application completely and stop the process, Environment.Exit(-1) must be called before the ending of the main method.

Points of Interest

This article enables you to handle any exceptions without forcingyour application to end due to unhandled exceptions in any case.

History

• 20^th October, 2009: Initial post

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

SHRIDHAR TL