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

Definición

Se produce cuando el control pierde el foco.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 
Atributos

Ejemplos

En el ejemplo de código siguiente se muestra cómo validar el texto de TextBox1.The following code example demonstrates validating the text for TextBox1. También muestra cómo tratar el LostFocus eventos estableciendo la FileDialog.InitialDirectory propiedad en el texto de TextBox1.It also demonstrates handling the LostFocus event by setting the FileDialog.InitialDirectory property to the text in TextBox1. El ejemplo de código usa el ErrorProvider.GetError método para comprobar si hay un error antes de abrir el cuadro de diálogo de archivo.The code example used the ErrorProvider.GetError method to check for an error before opening the file dialog box. Para ejecutar este ejemplo, pegue el código siguiente en un formulario que contenga un TextBox denominado TextBox1, un OpenFileDialog denominado OpenFileDialog1, un Button denominado Button1y un ErrorProvider denominado 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. Asegúrese de que todos los eventos están asociados con sus controladores de eventos.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

Comentarios

Al cambiar el foco mediante el teclado (ficha, MAYÚS+TAB etc.), mediante una llamada a la Select o SelectNextControl métodos, o estableciendo la ContainerControl.ActiveControl propiedad al formulario actual, se producen eventos de foco en el orden siguiente: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

Al cambiar el foco mediante el mouse o mediante una llamada a la Focus método, se producen eventos de foco en el orden siguiente: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

Si el CausesValidation propiedad está establecida en false, Validating y Validated se suprimen eventos.If the CausesValidation property is set to false, the Validating and Validated events are suppressed.

Si el Cancel propiedad de la CancelEventArgs está establecido en true en el Validating delegado de eventos, todos los eventos que se producirían generalmente después el Validating se suprimen eventos.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

El GotFocus y LostFocus son eventos de foco de bajo nivel que están vinculados a los mensajes de WM_KILLFOCUS y 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. Normalmente, el GotFocus y LostFocus eventos solo se usan al actualizar UICues o al escribir controles personalizados.Typically, the GotFocus and LostFocus events are only used when updating UICues or when writing custom controls. En su lugar el Enter y Leave eventos deben utilizarse para todos los controles, excepto el Form clase, que usa el Activated y Deactivate eventos.Instead the Enter and Leave events should be used for all controls except the Form class, which uses the Activated and Deactivate events. Para obtener más información sobre la GotFocus y LostFocus los eventos, vea el WM_KILLFOCUS y WM_KILLFOCUS temas.For more information about the GotFocus and LostFocus events, see the WM_KILLFOCUS and WM_KILLFOCUS topics.

Precaución

No intente establecer el foco desde el Enter, GotFocus, Leave, LostFocus, Validating, o Validated controladores de eventos.Do not attempt to set focus from within the Enter, GotFocus, Leave, LostFocus, Validating, or Validated event handlers. Si lo hace, puede provocar la aplicación o el sistema operativo deja de responder.Doing so can cause your application or the operating system to stop responding. Para obtener más información, consulte el WM_KILLFOCUS tema.For more information, see the WM_KILLFOCUS topic.

Para obtener más información sobre el manejo de eventos, consulte controlar y provocar eventos.For more information about handling events, see Handling and Raising Events.

Se aplica a

Consulte también: