Control.LostFocus Control.LostFocus Control.LostFocus Control.LostFocus Event

Definizione

Si verifica quando il controllo perde lo stato attivo.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 
Attributi

Esempi

Esempio di codice seguente illustra la convalida del testo per TextBox1.The following code example demonstrates validating the text for TextBox1. Inoltre descritta la gestione di LostFocus eventi impostando il FileDialog.InitialDirectory proprietà per il testo in TextBox1.It also demonstrates handling the LostFocus event by setting the FileDialog.InitialDirectory property to the text in TextBox1. L'esempio di codice utilizzato la ErrorProvider.GetError metodo per verificare la presenza di errori prima di aprire la finestra di dialogo file.The code example used the ErrorProvider.GetError method to check for an error before opening the file dialog box. Per eseguire questo esempio, incollare il codice seguente in un form contenente un TextBox denominato TextBox1, un OpenFileDialog denominato OpenFileDialog1, una Button denominata Button1e un ErrorProvider denominato ErrorProvider1.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. Verificare che tutti gli eventi sono associati i relativi gestori eventi.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

Commenti

Quando si modifica lo stato attivo usando la tastiera (TAB, MAIUSC + TAB e così via), chiamando il Select oppure SelectNextControl metodi, oppure impostando il ContainerControl.ActiveControl proprietà al form corrente, gli eventi dello stato attivo si verificano nell'ordine seguente: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

Quando si modifica lo stato attivo usando il mouse o chiamando il Focus metodo, gli eventi dello stato attivo si verificano nell'ordine seguente: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

Se il CausesValidation è impostata su false, il Validating e Validated gli eventi vengono soppressi.If the CausesValidation property is set to false, the Validating and Validated events are suppressed.

Se il Cancel proprietà del CancelEventArgs è impostata su true nel Validating delegato dell'evento, tutti gli eventi che in genere si verificano dopo il Validating eventi vengono soppressi.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.

Nota

Il GotFocus e LostFocus gli eventi sono eventi di attivazione di basso livello che sono associati ai messaggi di WM_KILLFOCUS e WM_SETFOCUS Windows.The GotFocus and LostFocus events are low-level focus events that are tied to the WM_KILLFOCUS and WM_SETFOCUS Windows messages. In genere, il GotFocus e LostFocus gli eventi vengono usati solo quando si aggiorna UICues o durante la scrittura di controlli personalizzati.Typically, the GotFocus and LostFocus events are only used when updating UICues or when writing custom controls. Invece il Enter e Leave gli eventi devono essere usati per tutti i controlli, ad eccezione di Form classe, che usa il Activated e Deactivate eventi.Instead the Enter and Leave events should be used for all controls except the Form class, which uses the Activated and Deactivate events. Per altre informazioni sul GotFocus e LostFocus eventi, vedere la WM_KILLFOCUS e WM_KILLFOCUS argomenti.For more information about the GotFocus and LostFocus events, see the WM_KILLFOCUS and WM_KILLFOCUS topics.

Attenzione

Non tentare di impostare lo stato attivo all'interno di Enter, GotFocus, Leave, LostFocus, Validating, o Validated gestori eventi.Do not attempt to set focus from within the Enter, GotFocus, Leave, LostFocus, Validating, or Validated event handlers. Questa operazione può causare l'applicazione o il sistema operativo smetterà di rispondere.Doing so can cause your application or the operating system to stop responding. Per altre informazioni, vedere la WM_KILLFOCUS argomento.For more information, see the WM_KILLFOCUS topic.

Per ulteriori informazioni sulla gestione degli eventi, consultare gestione e generazione di eventi.For more information about handling events, see Handling and Raising Events.

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