AsyncCompletedEventArgs.UserState 속성

정의

비동기 작업의 고유 식별자를 가져옵니다.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

속성 값

비동기 작업을 고유하게 식별하는 개체 참조이거나, 설정된 값이 없으면 null입니다.An object reference that uniquely identifies the asynchronous task; otherwise, null if no value has been set.

예제

다음 코드 예제에서는 AsyncOperation를 사용 하 여 비동기 작업의 수명을 추적 하는 방법을 보여 줍니다.The following code example demonstrates using an AsyncOperation to track the lifetime of asynchronous operations. 이 코드 예제는에 대해 제공 된 큰 예제의 일부는 System.ComponentModel.AsyncOperationManager 클래스입니다.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

설명

클래스가 여러 비동기 메서드를 지원 하거나 단일 메서드를 여러 번 호출 하는 경우 UserState 속성의 값을 확인 하 여 MethodNameCompleted 이벤트를 발생 시킨 작업을 확인할 수 있습니다.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. 코드에서의 해당 비동기 작업 시작 및 완료 태스크 Id 라고 하는 해당이 토큰을 추적 해야 합니다.Your code will need track these tokens, known as task IDs, as their corresponding asynchronous tasks start and complete.

이 속성의 값은 원래 작업을 시작 하는 비동기 메서드를 호출 하는 동안 설정 됩니다.The value of this property is set during the original call to the asynchronous method that started the task.

적용 대상

추가 정보