AsyncCompletedEventArgs.RaiseExceptionIfNecessary Metode

Definisi

Ruang nama:

System.ComponentModel

Rakitan:

System.ComponentModel.EventBasedAsync.dll

Sumber:

AsyncCompletedEvent.cs

Meningkatkan pengecualian yang disediakan pengguna jika operasi asinkron gagal.

protected:
 void RaiseExceptionIfNecessary();

protected void RaiseExceptionIfNecessary ();

member this.RaiseExceptionIfNecessary : unit -> unit

Protected Sub RaiseExceptionIfNecessary ()

Pengecualian

InvalidOperationException

Properti Cancelled adalah true.

TargetInvocationException

Properti Error telah ditetapkan oleh operasi asinkron. Properti InnerException menyimpan referensi ke Error.

Contoh

Contoh kode berikut menunjukkan penggunaan RaiseExceptionIfNecessary di properti kelas turunan.

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

Catatan Bagi Inheritor

Jika Anda telah memperoleh kelas Anda sendiri dari AsyncCompletedEventArgs kelas , properti baca-saja Anda harus memanggil RaiseExceptionIfNecessary() metode sebelum mengembalikan nilai properti. Jika kode pekerja asinkron komponen menetapkan pengecualian ke Error properti atau mengatur Cancelled properti ke true, properti akan memunculkan pengecualian jika klien mencoba membaca nilainya. Ini mencegah klien mengakses properti yang berpotensi tidak valid karena kegagalan dalam operasi asinkron.

Lihat juga

• AsyncOperationManager
• AsyncOperation
• Menerapkan Pola Asinkron Berbasis Peristiwa