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 se muestra cómo controlar LostFocus el evento 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. En el ejemplo de código ErrorProvider.GetError se usa el 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 TextBox1un TextBox denominado OpenFileDialog , OpenFileDialog1un denominado Button , Button1un denominado y ErrorProvider un ErrorProvider1denominado.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 estén asociados a 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 (Tab, Mayús + Tab, etc.), llamando a los Select métodos o SelectNextControl , o estableciendo la ContainerControl.ActiveControl propiedad en el formulario actual, los eventos de foco se producen 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 llamando al Focus método, los eventos de foco se producen 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 la CausesValidation propiedad se establece en false, se Validating suprimen los eventos y Validated .If the CausesValidation property is set to false, the Validating and Validated events are suppressed.

Si la Cancel CancelEventArgs propiedad de se establece true en en el Validating delegado de eventos, todos los eventos que se producirían normalmente Validating después del evento se suprimen.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

Los GotFocus eventos LostFocus y son eventos de foco de bajo nivel que están vinculados a los mensajes de Windows WM_KILLFOCUS y WM_SETFOCUS.The GotFocus and LostFocus events are low-level focus events that are tied to the WM_KILLFOCUS and WM_SETFOCUS Windows messages. Normalmente, los GotFocus eventos LostFocus y 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 Enter , Leave los eventos y deben usarse para todos los Form controles excepto la clase, Activated que Deactivate utiliza los eventos y.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 GotFocus los LostFocus eventos y, vea los temas sobre WM_KILLFOCUS y WM_KILLFOCUS .For more information about the GotFocus and LostFocus events, see the WM_KILLFOCUS and WM_KILLFOCUS topics.

Precaución

No intente establecer el foco desde Enterlos controladores de eventos, Leave GotFocus, LostFocus, Validating, o Validated .Do not attempt to set focus from within the Enter, GotFocus, Leave, LostFocus, Validating, or Validated event handlers. Esto puede hacer que la aplicación o el sistema operativo dejen de responder.Doing so can cause your application or the operating system to stop responding. Para obtener más información, vea el tema WM_KILLFOCUS .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: