AsyncCompletedEventArgs.Cancelled AsyncCompletedEventArgs.Cancelled AsyncCompletedEventArgs.Cancelled AsyncCompletedEventArgs.Cancelled Property

Definición

Obtiene un valor que indica si se ha cancelado una operación asincrónica.Gets a value indicating whether an asynchronous operation has been canceled.

public:
 property bool Cancelled { bool get(); };
public bool Cancelled { get; }
member this.Cancelled : bool
Public ReadOnly Property Cancelled As Boolean

Valor de propiedad

Es true si se canceló la operación en segundo plano; en caso contrario, es false.true if the background operation has been canceled; otherwise false. De manera predeterminada, es false.The default is false.

Ejemplos

AsyncOperation En el ejemplo de código siguiente se muestra el uso de para realizar un seguimiento de la duración de las operaciones asincrónicas.The following code example demonstrates the using an AsyncOperation to track the lifetime of asynchronous operations. Este ejemplo de código forma parte de un ejemplo más extenso proporcionado System.ComponentModel.AsyncOperationManager para la clase.This code example is part of a larger example provided for the System.ComponentModel.AsyncOperationManager class.

using System;
using System.Collections;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Globalization;
using System.Threading;
using System.Windows.Forms;
Imports System.Collections
Imports System.Collections.Specialized
Imports System.ComponentModel
Imports System.Drawing
Imports System.Globalization
Imports System.Threading
Imports System.Windows.Forms
// This event handler updates the ListView control when the
// PrimeNumberCalculator raises the CalculatePrimeCompleted
// event. The ListView item is updated with the appropriate
// outcome of the calculation: Canceled, Error, or result.
private void primeNumberCalculator1_CalculatePrimeCompleted(
    object sender, 
    CalculatePrimeCompletedEventArgs e)
{
    Guid taskId = (Guid)e.UserState;

    if (e.Cancelled)
    {   
        string result = "Canceled";

        ListViewItem lvi = UpdateListViewItem(taskId, result);

        if (lvi != null)
        {
            lvi.BackColor = Color.Pink;
            lvi.Tag = null;
        }
    }
    else if (e.Error != null)
    {
        string result = "Error";

        ListViewItem lvi = UpdateListViewItem(taskId, result);

        if (lvi != null)
        {
            lvi.BackColor = Color.Red;
            lvi.ForeColor = Color.White;
            lvi.Tag = null;
        }
    }
    else
    {   
        bool result = e.IsPrime;

        ListViewItem lvi = UpdateListViewItem(
            taskId, 
            result, 
            e.FirstDivisor);

        if (lvi != null)
        {
            lvi.BackColor = Color.LightGray;
            lvi.Tag = null;
        }
    }
}
' This event handler updates the ListView control when the
' PrimeNumberCalculator raises the CalculatePrimeCompleted
' event. The ListView item is updated with the appropriate
' outcome of the calculation: Canceled, Error, or result.
Private Sub primeNumberCalculator1_CalculatePrimeCompleted( _
    ByVal sender As Object, _
    ByVal e As CalculatePrimeCompletedEventArgs) _
    Handles primeNumberCalculator1.CalculatePrimeCompleted

    Dim taskId As Guid = CType(e.UserState, Guid)

    If e.Cancelled Then
        Dim result As String = "Canceled"

        Dim lvi As ListViewItem = UpdateListViewItem( _
            taskId, _
            result)

        If (lvi IsNot Nothing) Then
            lvi.BackColor = Color.Pink
            lvi.Tag = Nothing
        End If

    ElseIf e.Error IsNot Nothing Then

        Dim result As String = "Error"

        Dim lvi As ListViewItem = UpdateListViewItem( _
            taskId, result)

        If (lvi IsNot Nothing) Then
            lvi.BackColor = Color.Red
            lvi.ForeColor = Color.White
            lvi.Tag = Nothing
        End If
    Else
        Dim result As Boolean = e.IsPrime

        Dim lvi As ListViewItem = UpdateListViewItem( _
            taskId, _
            result, _
            e.FirstDivisor)

        If (lvi IsNot Nothing) Then
            lvi.BackColor = Color.LightGray
            lvi.Tag = Nothing
        End If
    End If

End Sub

Comentarios

Cuando la Cancelled propiedad es true, se interrumpió la operación asincrónica.When the Cancelled property is true, the asynchronous operation was interrupted.

El delegado de controlador de eventos de la aplicación cliente debe Cancelled comprobar la propiedad antes de obtener acceso a las propiedades de AsyncCompletedEventArgsuna clase derivada de; de lo contrario InvalidOperationException , la propiedad producirá una si la operación asincrónica fue interrumpa.The client application's event-handler delegate should check the Cancelled property before accessing any properties in a class derived from AsyncCompletedEventArgs; otherwise, the property will raise an InvalidOperationException if the asynchronous operation was interrupted.

Notas a los desarrolladores de herederos

Si proporciona propiedades de solo lectura en una clase derivada, asegúrese de llamar RaiseExceptionIfNecessary() al método.If you provide read-only properties in a derived class, be sure to call the RaiseExceptionIfNecessary() method. Esto evita que los clientes tengan acceso a las propiedades que no son válidas debido a un error en la operación asincrónica.This prevents clients from accessing properties that are potentially not valid due to a failure in the asynchronous operation.

Se aplica a

Consulte también: