AsyncCompletedEventArgs.UserState AsyncCompletedEventArgs.UserState AsyncCompletedEventArgs.UserState AsyncCompletedEventArgs.UserState Property

Definición

Obtiene el identificador único de la tarea asincrónica.Gets the unique identifier for the asynchronous task.

public:
 property System::Object ^ UserState { System::Object ^ get(); };
public object UserState { get; }
member this.UserState : obj
Public ReadOnly Property UserState As Object

Valor de propiedad

Referencia a un objeto que identifica de forma única la tarea asincrónica; de lo contrario, null si no se ha establecido ningún valor.An object reference that uniquely identifies the asynchronous task; otherwise, null if no value has been set.

Ejemplos

AsyncOperation En el ejemplo de código siguiente se muestra cómo utilizar para realizar el 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 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

Si una clase admite varios métodos asincrónicos o varias invocaciones de un único método, puede determinar qué tarea ha generado el evento MethodName Completed comprobando el valor de la UserState propiedad.If a class supports multiple asynchronous methods, or multiple invocations of a single method, you can determine which task raised the MethodNameCompleted event by checking the value of the UserState property. El código necesitará realizar un seguimiento de estos tokens, denominados identificadores de tarea, a medida que se inician y completan sus tareas asincrónicas correspondientes.Your code will need track these tokens, known as task IDs, as their corresponding asynchronous tasks start and complete.

El valor de esta propiedad se establece durante la llamada original al método asincrónico que inició la tarea.The value of this property is set during the original call to the asynchronous method that started the task.

Se aplica a

Consulte también: