Control.LostFocus Ereignis

Definition

Tritt ein, wenn das Steuerelement den Fokus verliert.Occurs when the control loses focus.

public:
 event EventHandler ^ LostFocus;
[System.ComponentModel.Browsable(false)]
public event EventHandler LostFocus;
member this.LostFocus : EventHandler 
Public Custom Event LostFocus As EventHandler 
Attribute

Beispiele

Im folgenden Codebeispiel wird das Validieren des Texts für textBox1 veranschaulicht.The following code example demonstrates validating the text for TextBox1. Außerdem wird die Behandlung des LostFocus-Ereignisses veranschaulicht, indem die Eigenschaft FileDialog.InitialDirectory auf den Text in TextBox1 festgelegt wird.It also demonstrates handling the LostFocus event by setting the FileDialog.InitialDirectory property to the text in TextBox1. Im Codebeispiel wurde die ErrorProvider.GetError-Methode verwendet, um vor dem Öffnen des Dialog Felds "Datei" einen Fehler zu überprüfen.The code example used the ErrorProvider.GetError method to check for an error before opening the file dialog box. Fügen Sie zum Ausführen dieses Beispiels den folgenden Code in ein Formular ein, das eine TextBox mit dem Namen TextBox1, eine OpenFileDialog namens OpenFileDialog1, eine Button mit dem Namen Button1und eine ErrorProvider mit dem Namen ErrorProvider1enthält.To run this example, paste the following code into a form containing a TextBox named TextBox1, an OpenFileDialog named OpenFileDialog1, a Button named Button1, and an ErrorProvider named ErrorProvider1. Stellen Sie sicher, dass alle Ereignisse ihren Ereignis Handlern zugeordnet sind.Ensure all events are associated with their event handlers.

private:
   void TextBox1_Validating( Object^ sender,
      System::ComponentModel::CancelEventArgs^ e )
   {
      // If nothing is entered,
      // an ArgumentException is caught; if an invalid directory is entered, 
      // a DirectoryNotFoundException is caught. An appropriate error message 
      // is displayed in either case.
      try
      {
         System::IO::DirectoryInfo^ directory = gcnew System::IO::DirectoryInfo( TextBox1->Text );
         directory->GetFiles();
         ErrorProvider1->SetError( TextBox1, "" );
      }
      catch ( System::ArgumentException^ ) 
      {
         ErrorProvider1->SetError( TextBox1, "Please enter a directory" );
      }
      catch ( System::IO::DirectoryNotFoundException^ ) 
      {
         ErrorProvider1->SetError( TextBox1, "The directory does not exist."
         "Try again with a different directory." );
      }
   }

   // This method handles the LostFocus event for TextBox1 by setting the 
   // dialog's InitialDirectory property to the text in TextBox1.
   void TextBox1_LostFocus( Object^ sender, System::EventArgs^ e )
   {
      OpenFileDialog1->InitialDirectory = TextBox1->Text;
   }

   // This method demonstrates using the ErrorProvider.GetError method 
   // to check for an error before opening the dialog box.
   void Button1_Click( System::Object^ sender, System::EventArgs^ e )
   {
      //If there is no error, then open the dialog box.
      if ( ErrorProvider1->GetError( TextBox1 )->Equals( "" ) )
      {
         ::DialogResult dialogResult = OpenFileDialog1->ShowDialog();
      }
   }
private void textBox1_Validating(object sender, 
    System.ComponentModel.CancelEventArgs e)
{
    // If nothing is entered,
    // an ArgumentException is caught; if an invalid directory is entered, 
    // a DirectoryNotFoundException is caught. An appropriate error message 
    // is displayed in either case.
    try
    {
        System.IO.DirectoryInfo directory = 
            new System.IO.DirectoryInfo(textBox1.Text);
        directory.GetFiles();
        errorProvider1.SetError(textBox1, "");

    }
    catch(System.ArgumentException ex1)
    {
        errorProvider1.SetError(textBox1, "Please enter a directory");

    }
    catch(System.IO.DirectoryNotFoundException ex2)
    {
        errorProvider1.SetError(textBox1, "The directory does not exist." +
            "Try again with a different directory.");
    }

}

// This method handles the LostFocus event for textBox1 by setting the 
// dialog's InitialDirectory property to the text in textBox1.
private void textBox1_LostFocus(object sender, System.EventArgs e)
{
    openFileDialog1.InitialDirectory = textBox1.Text;
}

// This method demonstrates using the ErrorProvider.GetError method 
// to check for an error before opening the dialog box.
private void button1_Click(System.Object sender, System.EventArgs e)
{
    //If there is no error, then open the dialog box.
    if (errorProvider1.GetError(textBox1)=="")
    {
        DialogResult dialogResult = openFileDialog1.ShowDialog();
    }
}
Private Sub TextBox1_Validating(ByVal sender As Object, _
ByVal e As System.ComponentModel.CancelEventArgs) _
Handles TextBox1.Validating

    ' If nothing is entered,
    ' an ArgumentException is caught; if an invalid directory is entered, 
    ' a DirectoryNotFoundException is caught. An appropriate error message 
    ' is displayed in either case.
    Try
        Dim directory As New System.IO.DirectoryInfo(TextBox1.Text)
        directory.GetFiles()
        ErrorProvider1.SetError(TextBox1, "")

    Catch ex1 As System.ArgumentException
        ErrorProvider1.SetError(TextBox1, "Please enter a directory")

    Catch ex2 As System.IO.DirectoryNotFoundException
        ErrorProvider1.SetError(TextBox1, _
        "The directory does not exist." & _
        "Try again with a different directory.")
    End Try

End Sub

' This method handles the LostFocus event for TextBox1 by setting the 
' dialog's InitialDirectory property to the text in TextBox1.
Private Sub TextBox1_LostFocus(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles TextBox1.LostFocus
    OpenFileDialog1.InitialDirectory = TextBox1.Text
End Sub


' This method demonstrates using the ErrorProvider.GetError method 
' to check for an error before opening the dialog box.
Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click

    'If there is no error, then open the dialog box.
    If ErrorProvider1.GetError(TextBox1) = "" Then
        Dim dialogResult As DialogResult = OpenFileDialog1.ShowDialog()
    End If

End Sub

Hinweise

Wenn Sie den Fokus mithilfe der Tastatur (Tab, UMSCHALT + TAB usw.) ändern, indem Sie die Methoden Select oder SelectNextControl aufrufen, oder indem Sie die Eigenschaft ContainerControl.ActiveControl auf das aktuelle Formular festlegen, treten Fokus Ereignisse in der folgenden Reihenfolge auf:When you change the focus by using the keyboard (TAB, SHIFT+TAB, and so on), by calling the Select or SelectNextControl methods, or by setting the ContainerControl.ActiveControl property to the current form, focus events occur in the following order:

  1. Enter

  2. GotFocus

  3. Leave

  4. Validating

  5. Validated

  6. LostFocus

Wenn Sie den Fokus mit der Maus oder durch Aufrufen der Focus-Methode ändern, treten Fokus Ereignisse in der folgenden Reihenfolge auf:When you change the focus by using the mouse or by calling the Focus method, focus events occur in the following order:

  1. Enter

  2. GotFocus

  3. LostFocus

  4. Leave

  5. Validating

  6. Validated

Wenn die CausesValidation-Eigenschaft auf false festgelegt ist, werden die Ereignisse Validating und Validated unterdrückt.If the CausesValidation property is set to false, the Validating and Validated events are suppressed.

Wenn die Cancel-Eigenschaft des CancelEventArgs im Validating-Ereignis Delegaten auf true festgelegt ist, werden alle Ereignisse, die normalerweise auftreten, nachdem das Validating-Ereignis unterdrückt wurde.If the Cancel property of the CancelEventArgs is set to true in the Validating event delegate, all events that would usually occur after the Validating event are suppressed.

Hinweis

Bei den GotFocus-und LostFocus Ereignissen handelt es sich um Schwerpunkt Ereignisse auf niedriger Ebene, die an die Windows-Meldungen WM_KILLFOCUS und WM_SETFOCUS gebunden sind.The GotFocus and LostFocus events are low-level focus events that are tied to the WM_KILLFOCUS and WM_SETFOCUS Windows messages. In der Regel werden die Ereignisse "GotFocus" und "LostFocus" nur beim Aktualisieren von UICues oder beim Schreiben von benutzerdefinierten Steuerelementen verwendet.Typically, the GotFocus and LostFocus events are only used when updating UICues or when writing custom controls. Stattdessen sollten die Ereignisse "Enter" und "Leave" für alle Steuerelemente mit Ausnahme der Form-Klasse verwendet werden, die die Activated-und Deactivate-Ereignisse verwendet.Instead the Enter and Leave events should be used for all controls except the Form class, which uses the Activated and Deactivate events. Weitere Informationen zu den GotFocus-und LostFocus Ereignissen finden Sie in den Themen WM_KILLFOCUS und WM_KILLFOCUS .For more information about the GotFocus and LostFocus events, see the WM_KILLFOCUS and WM_KILLFOCUS topics.

Achtung

Versuchen Sie nicht, den Fokus innerhalb der Ereignishandler "Enter", "GotFocus", "Leave", "LostFocus", "Validating" oder "Validated" festzulegen.Do not attempt to set focus from within the Enter, GotFocus, Leave, LostFocus, Validating, or Validated event handlers. Dies kann dazu führen, dass Ihre Anwendung oder das Betriebssystem nicht mehr reagiert.Doing so can cause your application or the operating system to stop responding. Weitere Informationen finden Sie im Thema WM_KILLFOCUS .For more information, see the WM_KILLFOCUS topic.

Weitere Informationen zur Behandlung von Ereignissen finden Sie unter behandeln und Auslösen von Ereignissen.For more information about handling events, see Handling and Raising Events.

Gilt für:

Siehe auch