Application.ThreadException Evento

public:
 static event System::Threading::ThreadExceptionEventHandler ^ ThreadException;

public static event System.Threading.ThreadExceptionEventHandler ThreadException;

member this.ThreadException : System.Threading.ThreadExceptionEventHandler 

Public Shared Custom Event ThreadException As ThreadExceptionEventHandler 

Tipo de Evento

Exemplos

O exemplo de código seguinte define os gestores de eventos para exceções que ocorrem em threads do Windows Forms e exceções que ocorrem noutros threads. Define SetUnhandledExceptionMode para que todas as exceções sejam tratadas pela aplicação, independentemente das definições no ficheiro de configuração do utilizador da aplicação. Utiliza o ThreadException evento para tratar exceções de threads UI e o UnhandledException evento para tratar exceções de threads não UI. Como UnhandledException não pode impedir a terminação de uma aplicação, o exemplo simplesmente regista o erro no registo de eventos da aplicação antes da terminação.

Este exemplo assume que definiu dois Button controlos, button1 e button2, na sua Form turma.

   // Creates a class to throw the error.
public:
   ref class ErrorHandler: public 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 gcnew ArgumentException( "The parameter was invalid" );
      }

   public:
      static void Main()
      {
         // Creates an instance of the methods that will handle the exception.
         CustomExceptionHandler ^ eh = gcnew CustomExceptionHandler;
         
         // Adds the event handler to the event.
         Application::ThreadException += gcnew ThreadExceptionEventHandler( eh, &Form1::CustomExceptionHandler::OnThreadException );
         
         // Runs the application.
         Application::Run( gcnew ErrorHandler );
      }
   };

   // Creates a class to handle the exception event.
internal:
   ref class CustomExceptionHandler
   {
      // Handles the exception event.
   public:
      void OnThreadException( Object^ /*sender*/, ThreadExceptionEventArgs^ t )
      {
         System::Windows::Forms::DialogResult result = ::DialogResult::Cancel;
         try
         {
            result = this->ShowThreadExceptionDialog( t->Exception );
         }
         catch ( Exception^ ) 
         {
            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:
      System::Windows::Forms::DialogResult ShowThreadExceptionDialog( Exception^ e )
      {
         String^ errorMsg = "An error occurred please contact the adminstrator with the following information:\n\n";
         errorMsg = String::Concat( errorMsg, e->Message, "\n\nStack Trace:\n", e->StackTrace );
         return MessageBox::Show( errorMsg, "Application Error", MessageBoxButtons::AbortRetryIgnore, MessageBoxIcon::Stop );
      }
   };

Thread newThread = null;

// Starts the application.
public static void Main(string[] args)
{
    // Add the event handler for handling UI thread exceptions to the event.
    Application.ThreadException += new ThreadExceptionEventHandler(ErrorHandlerForm.Form1_UIThreadException);

    // Set the unhandled exception mode to force all Windows Forms errors to go through
    // our handler.
    Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException);

    // Add the event handler for handling non-UI thread exceptions to the event.
    AppDomain.CurrentDomain.UnhandledException +=
        new UnhandledExceptionEventHandler(CurrentDomain_UnhandledException);

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

// 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");
}

// Start a new thread, separate from Windows Forms, that will throw an exception.
private void button2_Click(object sender, System.EventArgs e)
{
    ThreadStart newThreadStart = new ThreadStart(newThread_Execute);
    newThread = new Thread(newThreadStart);
    newThread.Start();
}

// The thread we start up to demonstrate non-UI exception handling.
void newThread_Execute()
{
    throw new Exception("The method or operation is not implemented.");
}

// Handle the UI exceptions by showing a dialog box, and asking the user whether
// or not they wish to abort execution.
private static void Form1_UIThreadException(object sender, ThreadExceptionEventArgs t)
{
    DialogResult result = DialogResult.Cancel;
    try
    {
        result = ShowThreadExceptionDialog("Windows Forms Error", t.Exception);
    }
    catch
    {
        try
        {
            MessageBox.Show("Fatal Windows Forms Error",
                "Fatal Windows Forms Error", MessageBoxButtons.AbortRetryIgnore, MessageBoxIcon.Stop);
        }
        finally
        {
            Application.Exit();
        }
    }

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

// Handle the UI exceptions by showing a dialog box, and asking the user whether
// or not they wish to abort execution.
// NOTE: This exception cannot be kept from terminating the application - it can only
// log the event, and inform the user about it.
private static void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
{
    try
    {
        Exception ex = (Exception)e.ExceptionObject;
        string errorMsg = "An application error occurred. Please contact the adminstrator " +
            "with the following information:\n\n";

        // Since we can't prevent the app from terminating, log this to the event log.
        if (!EventLog.SourceExists("ThreadException"))
        {
            EventLog.CreateEventSource("ThreadException", "Application");
        }

        // Create an EventLog instance and assign its source.
        EventLog myLog = new EventLog();
        myLog.Source = "ThreadException";
        myLog.WriteEntry(errorMsg + ex.Message + "\n\nStack Trace:\n" + ex.StackTrace);
    }
    catch (Exception exc)
    {
        try
        {
            MessageBox.Show("Fatal Non-UI Error",
                "Fatal Non-UI Error. Could not write the error to the event log. Reason: "
                + exc.Message, MessageBoxButtons.OK, MessageBoxIcon.Stop);
        }
        finally
        {
            Application.Exit();
        }
    }
}

// Creates the error message and displays it.
private static DialogResult ShowThreadExceptionDialog(string title, Exception e)
{
    string errorMsg = "An application 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, title, MessageBoxButtons.AbortRetryIgnore,
        MessageBoxIcon.Stop);
}

Private newThread As Thread = Nothing

' Starts the application. 
<SecurityPermission(SecurityAction.Demand, Flags:=SecurityPermissionFlag.ControlAppDomain)> _
Public Shared Sub Main()
    ' Add the event handler for handling UI thread exceptions to the event.
    AddHandler Application.ThreadException, AddressOf ErrorHandlerForm.Form1_UIThreadException

    ' Set the unhandled exception mode to force all Windows Forms errors to go through
    ' our handler.
    Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException)

    ' Add the event handler for handling non-UI thread exceptions to the event. 
    AddHandler AppDomain.CurrentDomain.UnhandledException, AddressOf CurrentDomain_UnhandledException

    ' Runs the application.
    Application.Run(New ErrorHandlerForm())
End Sub


' Programs the button to throw an exception when clicked.
Private Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles button1.Click
    Throw New ArgumentException("The parameter was invalid")
End Sub

' Start a new thread, separate from Windows Forms, that will throw an exception.
Private Sub button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles button2.Click
    Dim newThreadStart As New ThreadStart(AddressOf newThread_Execute)
    newThread = New Thread(newThreadStart)
    newThread.Start()
End Sub


' The thread we start up to demonstrate non-UI exception handling. 
Sub newThread_Execute()
    Throw New Exception("The method or operation is not implemented.")
End Sub


' Handle the UI exceptions by showing a dialog box, and asking the user whether
' or not they wish to abort execution.
Private Shared Sub Form1_UIThreadException(ByVal sender As Object, ByVal t As ThreadExceptionEventArgs)
    Dim result As System.Windows.Forms.DialogResult = _
        System.Windows.Forms.DialogResult.Cancel
    Try
        result = ShowThreadExceptionDialog("Windows Forms Error", t.Exception)
    Catch
        Try
            MessageBox.Show("Fatal Windows Forms Error", _
                "Fatal Windows Forms Error", MessageBoxButtons.AbortRetryIgnore, MessageBoxIcon.Stop)
        Finally
            Application.Exit()
        End Try
    End Try

    ' Exits the program when the user clicks Abort.
    If result = DialogResult.Abort Then
        Application.Exit()
    End If
End Sub

' Handle the UI exceptions by showing a dialog box, and asking the user whether
' or not they wish to abort execution.
' NOTE: This exception cannot be kept from terminating the application - it can only 
' log the event, and inform the user about it. 
Private Shared Sub CurrentDomain_UnhandledException(ByVal sender As Object, _
ByVal e As UnhandledExceptionEventArgs)
    Try
        Dim ex As Exception = CType(e.ExceptionObject, Exception)
        Dim errorMsg As String = "An application error occurred. Please contact the adminstrator " & _
            "with the following information:" & ControlChars.Lf & ControlChars.Lf

        ' Since we can't prevent the app from terminating, log this to the event log.
        If (Not EventLog.SourceExists("ThreadException")) Then
            EventLog.CreateEventSource("ThreadException", "Application")
        End If

        ' Create an EventLog instance and assign its source.
        Dim myLog As New EventLog()
        myLog.Source = "ThreadException"
        myLog.WriteEntry((errorMsg + ex.Message & ControlChars.Lf & ControlChars.Lf & _
            "Stack Trace:" & ControlChars.Lf & ex.StackTrace))
    Catch exc As Exception
        Try
            MessageBox.Show("Fatal Non-UI Error", "Fatal Non-UI Error. Could not write the error to the event log. " & _
                "Reason: " & exc.Message, MessageBoxButtons.OK, MessageBoxIcon.Stop)
        Finally
            Application.Exit()
        End Try
    End Try
End Sub


' Creates the error message and displays it.
Private Shared Function ShowThreadExceptionDialog(ByVal title As String, ByVal e As Exception) As DialogResult
    Dim errorMsg As String = "An application error occurred. Please contact the adminstrator " & _
 "with the following information:" & ControlChars.Lf & ControlChars.Lf
    errorMsg = errorMsg & e.Message & ControlChars.Lf & _
 ControlChars.Lf & "Stack Trace:" & ControlChars.Lf & e.StackTrace

    Return MessageBox.Show(errorMsg, title, MessageBoxButtons.AbortRetryIgnore, MessageBoxIcon.Stop)
End Function

Observações

Este evento permite que a sua aplicação Windows Forms trate exceções que de outra forma não seriam tratadas e que ocorrem em threads do Windows Forms. Anexe o seu gestor de eventos ao ThreadException evento para lidar com estas exceções, o que deixará a sua candidatura num estado desconhecido. Sempre que possível, as exceções devem ser tratadas por um bloco estruturado de tratamento de exceções.

Pode alterar se este callback é usado para exceções de thread Windows Forms não tratadas definindo SetUnhandledExceptionMode. Para detetar exceções que ocorrem em threads que não foram criados e não pertencem a Windows Forms, use o handler de eventos UnhandledException.