Application.ThreadException Evento

Definizione

Spazio dei nomi:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Si verifica quando viene generata un'eccezione non intercettata dal thread.

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 evento

ThreadExceptionEventHandler

Esempio

L'esempio di codice seguente imposta i gestori eventi per le eccezioni che si verificano in Windows Forms thread ed eccezioni che si verificano in altri thread. Imposta in SetUnhandledExceptionMode modo che tutte le eccezioni vengano gestite dall'applicazione, indipendentemente dalle impostazioni nel file di configurazione utente dell'applicazione. Usa l'evento ThreadException per gestire le eccezioni del thread dell'interfaccia utente e l'evento UnhandledException per gestire le eccezioni di thread non dell'interfaccia utente. Poiché UnhandledException non è possibile impedire a un'applicazione di terminare, l'esempio registra semplicemente l'errore nel registro eventi dell'applicazione prima della chiusura.

In questo esempio si presuppone che nella classe siano stati definiti due Button controlli button1 e button2.Form

   // 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

Commenti

Questo evento consente all'applicazione Windows Forms di gestire eccezioni altrimenti non gestite che si verificano in Windows Forms thread. Collegare il gestore eventi all'evento ThreadException per gestire queste eccezioni, che lascerà l'applicazione in uno stato sconosciuto. Laddove possibile, le eccezioni devono essere gestite da un blocco di gestione delle eccezioni strutturato.

È possibile modificare se questo callback viene usato per le eccezioni di thread non gestite Windows Forms impostando SetUnhandledExceptionMode. Per rilevare le eccezioni che si verificano nei thread non create e di proprietà di Windows Forms, usare il UnhandledException gestore eventi.

Nota

Per garantire che non vengano perse attivazioni di questo evento, è necessario associare un gestore prima di chiamare Application.Run.

Nota

A questo evento può essere associato un solo gestore. Se vengono aggiunti più gestori, solo il gestore aggiunto più di recente verrà chiamato su un'eccezione non gestita.

Attenzione

Poiché si tratta di un evento statico, è necessario scollegare i gestori eventi quando l'applicazione viene eliminata o le perdite di memoria genereranno perdite di memoria.