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Application.ThreadException Event

Occurs when an untrapped thread exception is thrown.

Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)

public static event ThreadExceptionEventHandler ThreadException
/** @event */
public static void add_ThreadException (ThreadExceptionEventHandler value)

/** @event */
public static void remove_ThreadException (ThreadExceptionEventHandler value)

JScript supports the use of events, but not the declaration of new ones.

This event allows your Windows Forms application to handle otherwise unhandled exceptions. Attach your event handlers to the ThreadException event to deal with these exceptions, which will leave your application in an unknown state. Where possible, exceptions should be handled by a structured exception handling block.

The following code example raises a ThreadException event when button1 on the form is clicked. The example creates two classes. The ErrorHandler class creates the form and button that raises the event. The CustomExceptionHandler class provides the methods to handle the exception.

In Main in the ErrorHandler class, the code creates a new instance of the exception handling class, that is, an instance of the CustomExceptionHandler. Then the instance is added to the event, and the application is run.

In the OnThreadException method in the CustomExceptionHandler class, the example uses a try...catch...finally statement to process the exception. The ShowThreadExceptionDialog method creates the message to display, and displays it in a message box.

// Creates a class to throw the error.
 public class ErrorHandler : System.Windows.Forms.Form {
 
    // Inserts the code to create a form with a button.
 
    // Programs the button to throw an exception when clicked.
    private void button1_Click(object sender, System.EventArgs e) {
       throw new ArgumentException("The parameter was invalid");
    }
 
    public static void Main(string[] args) {
       // Creates an instance of the methods that will handle the exception.
       CustomExceptionHandler eh = new CustomExceptionHandler();
 
       // Adds the event handler to to the event.
       Application.ThreadException += new ThreadExceptionEventHandler(eh.OnThreadException);
 
       // Runs the application.
       Application.Run(new ErrorHandler());
    }
 }
 
 // Creates a class to handle the exception event.
 internal class CustomExceptionHandler {
 
    // Handles the exception event.
    public void OnThreadException(object sender, ThreadExceptionEventArgs t) 
    {
       DialogResult result = DialogResult.Cancel;
       try
       {
          result = this.ShowThreadExceptionDialog(t.Exception);
       }
       catch
       {
          try
          {
             MessageBox.Show("Fatal Error", "Fatal Error", MessageBoxButtons.AbortRetryIgnore, MessageBoxIcon.Stop);
          }
          finally
          {
             Application.Exit();
          }
       }

       // Exits the program when the user clicks Abort.
       if (result == DialogResult.Abort) 
          Application.Exit();
    }
 
    // Creates the error message and displays it.
    private DialogResult ShowThreadExceptionDialog(Exception e) {
       string errorMsg = "An error occurred please contact the adminstrator with the following information:\n\n";
       errorMsg = errorMsg + e.Message + "\n\nStack Trace:\n" + e.StackTrace;
       return MessageBox.Show(errorMsg, "Application Error", MessageBoxButtons.AbortRetryIgnore, MessageBoxIcon.Stop);
    }
 }


// Creates a class to throw the error.
public static class ErrorHandler extends System.Windows.Forms.Form
{
    // Inserts the code to create a form with a button.
    // Programs the button to throw an exception when clicked.
    private void button1_Click(Object sender, System.EventArgs e)
    {
        throw new ArgumentException("The parameter was invalid");
    } //button1_Click

    public static void main(String[] args)
    {
        // Creates an instance of the methods that will handle 
        // the exception.
        CustomExceptionHandler eh = new CustomExceptionHandler();

        // Adds the event handler to to the event.
        Application.add_ThreadException(
            new ThreadExceptionEventHandler(eh.OnThreadException));

        // Runs the application.
        Application.Run(new ErrorHandler());
    } //main
} //ErrorHandler

// Creates a class to handle the exception event.
static class CustomExceptionHandler
{
    // Handles the exception event.
    public void OnThreadException(Object sender, ThreadExceptionEventArgs t)
    {
        DialogResult result = DialogResult.Cancel;
        try {
            result = this.ShowThreadExceptionDialog(t.get_Exception());
        }
        catch (System.Exception exp) {
            try {
                MessageBox.Show("Fatal Error", "Fatal Error", 
                    MessageBoxButtons.AbortRetryIgnore, 
                    MessageBoxIcon.Stop);
            }
            finally {
                Application.Exit();
            }
        }

        // Exits the program when the user clicks Abort.
        if (result.Equals(DialogResult.Abort)) {
            Application.Exit();
        }
    } //OnThreadException

    // Creates the error message and displays it.
    private DialogResult ShowThreadExceptionDialog(System.Exception e)
    {
        String errorMsg = "An error occurred please contact the"
            + " administrator with the following information:\n\n";
        errorMsg = errorMsg + e.get_Message() + "\n\nStack Trace:\n"
            + e.get_StackTrace();
        return MessageBox.Show(errorMsg, "Application Error",
            MessageBoxButtons.AbortRetryIgnore, MessageBoxIcon.Stop);
    } //ShowThreadExceptionDialog
} //CustomExceptionHandler

public static void main(String[] args)
{
    ErrorHandler.main(args);
}//main

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0
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