AsyncCompletedEventArgs.RaiseExceptionIfNecessary Method

Definition

Genera un'eccezione fornita dall'utente in caso di errore in un'operazione asincrona.Raises a user-supplied exception if an asynchronous operation failed.

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

Exceptions

La proprietà Cancelled è true.The Cancelled property is true.

La proprietà Error è stata impostata dall'operazione asincrona.The Error property has been set by the asynchronous operation. La proprietà InnerException contiene un riferimento a Error.The InnerException property holds a reference to Error.

Examples

Nell'esempio di codice riportato di seguito viene illustrato l'utilizzo di RaiseExceptionIfNecessary nelle proprietà della classe derivata.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

Notes to Inheritors

Se è stata derivata la classe dalla classe AsyncCompletedEventArgs, le proprietà di sola lettura devono chiamare il metodo RaiseExceptionIfNecessary() prima di restituire il valore della proprietà.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. Se il codice di lavoro asincrono del componente assegna un'eccezione alla proprietà Error o imposta la proprietà Cancelled su true, la proprietà genererà un'eccezione se un client tenta di leggere il relativo valore.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. Ciò impedisce ai client di accedere a proprietà potenzialmente non valide a causa di un errore nell'operazione asincrona.This prevents clients from accessing properties that are potentially not valid due to a failure in the asynchronous operation.

Applies to

See also