AsyncCompletedEventArgs.Error Propiedad

Definición

Obtiene un valor que indica el error que se produjo durante una operación asincrónica.Gets a value indicating which error occurred during an asynchronous operation.

public:
 property Exception ^ Error { Exception ^ get(); };
public Exception Error { get; }
member this.Error : Exception
Public ReadOnly Property Error As Exception

Valor de propiedad

Instancia de Exception, si se ha producido un error durante una operación asincrónica; de lo contrario, null.An Exception instance, if an error occurred during an asynchronous operation; otherwise null.

Ejemplos

En el ejemplo de código siguiente se muestra cómo usar un AsyncOperation para realizar un seguimiento de la duración de las operaciones asincrónicas.The following code example demonstrates using an AsyncOperation to track the lifetime of asynchronous operations. Este ejemplo de código forma parte de un ejemplo más extenso proporcionado para la clase System.ComponentModel.AsyncOperationManager.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

Si se produce una excepción durante una operación asincrónica, la clase asignará la excepción a la propiedad Error.If an exception is raised during an asynchronous operation, the class will assign the exception to the Error property. El delegado de controlador de eventos de la aplicación cliente debe comprobar la propiedad Error antes de tener acceso a las propiedades de una clase derivada de AsyncCompletedEventArgs; de lo contrario, la propiedad generará un TargetInvocationException con su propiedad InnerException que contiene una referencia a Error.The client application's event-handler delegate should check the Error property before accessing any properties in a class derived from AsyncCompletedEventArgs; otherwise, the property will raise a TargetInvocationException with its InnerException property holding a reference to Error.

El valor de la propiedad Error se null si se canceló la operación.The value of the Error property is null if the operation was canceled.

Notas a los desarrolladores de herederos

Si proporciona propiedades de solo lectura en una clase derivada, asegúrese de llamar al método RaiseExceptionIfNecessary() en la implementación de la propiedad.If you provide read-only properties in a derived class, be sure to call the RaiseExceptionIfNecessary() method in your property implementation. 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: