AsyncCompletedEventArgs.RaiseExceptionIfNecessary Methode

Definition

Löst eine benutzerdefinierte Ausnahme aus, wenn bei einem asynchronen Vorgang ein Fehler aufgetreten ist.Raises a user-supplied exception if an asynchronous operation failed.

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

Ausnahmen

Die Cancelled-Eigenschaft ist true.The Cancelled property is true.

Die Error-Eigenschaft wurde durch den asynchronen Vorgang festgelegt.The Error property has been set by the asynchronous operation. Die InnerException-Eigenschaft enthält einen Verweis auf Error.The InnerException property holds a reference to Error.

Beispiele

Im folgenden Codebeispiel wird die RaiseExceptionIfNecessary Verwendung von in abgeleiteten Klasseneigenschaften veranschaulicht.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

Hinweise für Vererber

Wenn Sie eine eigene Klasse von der AsyncCompletedEventArgs -Klasse abgeleitet haben, sollten die schreibgeschützten Eigenschaften die RaiseExceptionIfNecessary() -Methode vor dem Zurückgeben des Eigenschafts Werts abrufen.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. Wenn der asynchrone Workercode der Komponente der- Error Eigenschaft eine Ausnahme zuweist oder die Cancelled - trueEigenschaft auf festlegt, wird von der-Eigenschaft eine Ausnahme ausgelöst, wenn ein Client versucht, seinen Wert zu lesen.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. Dadurch wird verhindert, dass Clients auf Eigenschaften zugreifen, die aufgrund eines Fehlers im asynchronen Vorgang möglicherweise nicht gültig sind.This prevents clients from accessing properties that are potentially not valid due to a failure in the asynchronous operation.

Gilt für:

Siehe auch