AsyncCompletedEventArgs.RaiseExceptionIfNecessary Метод

Определение

Вызывает предоставленное пользователем исключение в случае неудачного выполнения асинхронной операции.Raises a user-supplied exception if an asynchronous operation failed.

protected:
 void RaiseExceptionIfNecessary();
protected void RaiseExceptionIfNecessary ();
member this.RaiseExceptionIfNecessary : unit -> unit
Protected Sub RaiseExceptionIfNecessary ()

Исключения

Значение свойства Cancelledtrue.The Cancelled property is true.

Свойство Error было установлено асинхронной операцией.The Error property has been set by the asynchronous operation. Свойство InnerException содержит ссылку на ошибку Error.The InnerException property holds a reference to Error.

Примеры

В следующем примере кода показано использование RaiseExceptionIfNecessary в свойствах производного класса.The following code example demonstrates using RaiseExceptionIfNecessary in derived class properties.

public class CalculatePrimeCompletedEventArgs :
    AsyncCompletedEventArgs
{
    private int numberToTestValue = 0;
    private int firstDivisorValue = 1;
    private bool isPrimeValue;

    public CalculatePrimeCompletedEventArgs(
        int numberToTest,
        int firstDivisor,
        bool isPrime,
        Exception e,
        bool canceled,
        object state) : base(e, canceled, state)
    {
        this.numberToTestValue = numberToTest;
        this.firstDivisorValue = firstDivisor;
        this.isPrimeValue = isPrime;
    }

    public int NumberToTest
    {
        get
        {
            // Raise an exception if the operation failed or 
            // was canceled.
            RaiseExceptionIfNecessary();

            // If the operation was successful, return the 
            // property value.
            return numberToTestValue;
        }
    }

    public int FirstDivisor
    {
        get
        {
            // Raise an exception if the operation failed or 
            // was canceled.
            RaiseExceptionIfNecessary();

            // If the operation was successful, return the 
            // property value.
            return firstDivisorValue;
        }
    }

    public bool IsPrime
    {
        get
        {
            // Raise an exception if the operation failed or 
            // was canceled.
            RaiseExceptionIfNecessary();

            // If the operation was successful, return the 
            // property value.
            return isPrimeValue;
        }
    }
}

Public Class CalculatePrimeCompletedEventArgs
    Inherits AsyncCompletedEventArgs
    Private numberToTestValue As Integer = 0
    Private firstDivisorValue As Integer = 1
    Private isPrimeValue As Boolean


    Public Sub New( _
    ByVal numberToTest As Integer, _
    ByVal firstDivisor As Integer, _
    ByVal isPrime As Boolean, _
    ByVal e As Exception, _
    ByVal canceled As Boolean, _
    ByVal state As Object)

        MyBase.New(e, canceled, state)
        Me.numberToTestValue = numberToTest
        Me.firstDivisorValue = firstDivisor
        Me.isPrimeValue = isPrime

    End Sub


    Public ReadOnly Property NumberToTest() As Integer
        Get
            ' Raise an exception if the operation failed 
            ' or was canceled.
            RaiseExceptionIfNecessary()

            ' If the operation was successful, return 
            ' the property value.
            Return numberToTestValue
        End Get
    End Property


    Public ReadOnly Property FirstDivisor() As Integer
        Get
            ' Raise an exception if the operation failed 
            ' or was canceled.
            RaiseExceptionIfNecessary()

            ' If the operation was successful, return 
            ' the property value.
            Return firstDivisorValue
        End Get
    End Property


    Public ReadOnly Property IsPrime() As Boolean
        Get
            ' Raise an exception if the operation failed 
            ' or was canceled.
            RaiseExceptionIfNecessary()

            ' If the operation was successful, return 
            ' the property value.
            Return isPrimeValue
        End Get
    End Property
End Class

Примечания для тех, кто наследует этот метод

Если вы настроили собственный класс из класса AsyncCompletedEventArgs, то свойства только для чтения должны вызывать метод RaiseExceptionIfNecessary() перед возвратом значения свойства.If you have derived your own class from the AsyncCompletedEventArgs class, your read-only properties should call the RaiseExceptionIfNecessary() method before returning the property value. Если асинхронный рабочий процесс компонента присваивает исключение свойству Error или устанавливает для свойства Cancelled значение true, свойство вызывает исключение, если клиент пытается прочитать его значение.If the component's asynchronous worker code assigns an exception to the Error property or sets the Cancelled property to true, the property will raise an exception if a client tries to read its value. Это предотвращает доступ клиентов к свойствам, которые потенциально недействительны из-за сбоя в асинхронной операции.This prevents clients from accessing properties that are potentially not valid due to a failure in the asynchronous operation.

Применяется к

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