AsyncCompletedEventArgs.RaiseExceptionIfNecessary Metod

Definition

Namnområde:
System.ComponentModel
Sammansättningar:
System.dll, System.ComponentModel.EventBasedAsync.dll
Sammansättning:
System.dll
Sammansättning:
netstandard.dll

Genererar ett undantag från användaren om en asynkron åtgärd misslyckades.

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

Undantag

InvalidOperationException

Egenskapen Cancelled är true.

TargetInvocationException

Egenskapen Error har angetts av den asynkrona åtgärden. Egenskapen InnerException innehåller en referens till Error.

Exempel

Följande kodexempel visar hur du använder RaiseExceptionIfNecessary i härledda klassegenskaper.

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

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

Anteckningar till arvingar

Om du har härlett din egen klass från AsyncCompletedEventArgs klassen bör dina skrivskyddade egenskaper anropa RaiseExceptionIfNecessary() metoden innan du returnerar egenskapsvärdet. Om komponentens asynkrona arbetskod tilldelar ett undantag till Error egenskapen eller anger Cancelled egenskapen till trueskapar egenskapen ett undantag om en klient försöker läsa dess värde. Detta hindrar klienter från att komma åt egenskaper som potentiellt inte är giltiga på grund av ett fel i den asynkrona åtgärden.

Gäller för

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