DataServiceContext.EndExecute<TElement>(IAsyncResult) Metod

public:
generic <typename TElement>
 System::Collections::Generic::IEnumerable<TElement> ^ EndExecute(IAsyncResult ^ asyncResult);

public System.Collections.Generic.IEnumerable<TElement> EndExecute<TElement>(IAsyncResult asyncResult);

member this.EndExecute : IAsyncResult -> seq<'Element>

Public Function EndExecute(Of TElement) (asyncResult As IAsyncResult) As IEnumerable(Of TElement)

Typparametrar

Parametrar

Returer

Resultatet som returneras av frågeåtgärden.

Undantag

Exempel

I följande exempel visas hur du kör en asynkron fråga genom att anropa BeginExecute metoden för att starta frågan. Det infogade ombudet EndExecute anropar metoden för att visa frågeresultatet. I det här exemplet används det DataServiceContext som genereras av verktyget Lägg till tjänstreferens baserat på Northwind-datatjänsten, som skapas när du slutför WCF Data Services .

public static void BeginExecuteCustomersQuery()
{
    // Create the DataServiceContext using the service URI.
    NorthwindEntities context = new NorthwindEntities(svcUri);

    // Define the query to execute asynchronously that returns
    // all customers with their respective orders.
    DataServiceQuery<Customer> query = (DataServiceQuery<Customer>)(from cust in context.Customers.Expand("Orders")
                                       where cust.CustomerID == "ALFKI"
                                       select cust);

    try
    {
        // Begin query execution, supplying a method to handle the response
        // and the original query object to maintain state in the callback.
        query.BeginExecute(OnCustomersQueryComplete, query);
    }
    catch (DataServiceQueryException ex)
    {
        throw new ApplicationException(
            "An error occurred during query execution.", ex);
    }
}

// Handle the query callback.
private static void OnCustomersQueryComplete(IAsyncResult result)
{
    // Get the original query from the result.
    DataServiceQuery<Customer> query =
        result as DataServiceQuery<Customer>;

    foreach (Customer customer in query.EndExecute(result))
    {
        Console.WriteLine("Customer Name: {0}", customer.CompanyName);
        foreach (Order order in customer.Orders)
        {
            Console.WriteLine("Order #: {0} - Freight $: {1}",
                order.OrderID, order.Freight);
        }
    }
}

Public Shared Sub BeginExecuteCustomersQuery()
    ' Create the DataServiceContext using the service URI.
    Dim context = New NorthwindEntities(svcUri)

    ' Define the delegate to callback into the process
    Dim callback As AsyncCallback = AddressOf OnCustomersQueryComplete

    ' Define the query to execute asynchronously that returns 
    ' all customers with their respective orders.
    Dim query As DataServiceQuery(Of Customer) =
    context.Customers.Expand("Orders")

    Try
        ' Begin query execution, supplying a method to handle the response
        ' and the original query object to maintain state in the callback.
        query.BeginExecute(callback, query)
    Catch ex As DataServiceQueryException
        Throw New ApplicationException(
                "An error occurred during query execution.", ex)
    End Try
End Sub
' Handle the query callback.
Private Shared Sub OnCustomersQueryComplete(ByVal result As IAsyncResult)
    ' Get the original query from the result.
    Dim query As DataServiceQuery(Of Customer) =
        CType(result.AsyncState, DataServiceQuery(Of Customer))

    ' Complete the query execution.
    For Each customer As Customer In query.EndExecute(result)
        Console.WriteLine("Customer Name: {0}", customer.CompanyName)
        For Each order As Order In customer.Orders
            Console.WriteLine("Order #: {0} - Freight $: {1}",
                    order.OrderID, order.Freight)
        Next
    Next
End Sub

Kommentarer

Enligt standardmönstret för asynkron start-end anropas det angivna återanropet när frågeresultat hämtas. Mer information finns i Asynkrona åtgärder.

När återanropet anropas har alla resultat lästs från HTTP-strömmen, men de har inte bearbetats. inga lokala användarriktade objekt har materialiserats eller ändrats och identitetsmatchning har inte inträffat. När EndExecute anropas skapas och returneras en DataServiceResponse , men resultatet har fortfarande inte bearbetats. Identitetsmatchning, objektmaterialisering och manipulering sker endast när användaren räknar upp resultaten.

Se även

• Anvisningar: Köra Asynkrona datatjänstfrågor (WCF Data Services)