TaskExtensions.Unwrap Metodo

Definizione

Spazio dei nomi:

System.Threading.Tasks

Assembly:

System.Runtime.dll

Overload

Unwrap(Task<Task>)	Crea un oggetto Task proxy che rappresenta l'operazione asincrona di un oggetto Task<Task> (C#) o Task (Of Task) (Visual Basic).
Unwrap<TResult>(Task<Task<TResult>>)	Crea un oggetto Task proxy che rappresenta l'operazione asincrona di un oggetto Task<Task<T>> (C#) o Task (Of Task(Of T)) (Visual Basic).

Unwrap(Task<Task>)

Origine:

TaskExtensions.cs

Crea un oggetto Task proxy che rappresenta l'operazione asincrona di un oggetto Task<Task> (C#) o Task (Of Task) (Visual Basic).

public:
[System::Runtime::CompilerServices::Extension]
 static System::Threading::Tasks::Task ^ Unwrap(System::Threading::Tasks::Task<System::Threading::Tasks::Task ^> ^ task);

public static System.Threading.Tasks.Task Unwrap (this System.Threading.Tasks.Task<System.Threading.Tasks.Task> task);

static member Unwrap : System.Threading.Tasks.Task<System.Threading.Tasks.Task> -> System.Threading.Tasks.Task

<Extension()>
Public Function Unwrap (task As Task(Of Task)) As Task

Parametri

task

Task<Task>

Oggetto Task<Task> (C#) o Task (Of Task) (Visual Basic) di cui annullare il wrapping.

Restituisce

Task

Attività che rappresenta l'operazione asincrona dell'oggetto System.Threading.Tasks.Task(Of Task) fornito.

Eccezioni

ArgumentNullException

Eccezione generata se l'argomento task è Null.

Esempio

L'esempio seguente illustra come annullare il wrapping di un'attività:

using System;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;

class UnWrapDemo
{
     // Demonstrated features:
        //		Task.Unwrap()
        // 		Task.Factory.StartNew()
        //		Task.ContinueWith()
        // Expected results:
        // 		Indicates that continuation chains can be set up virtually instantaneously using Unwrap(), and then left to run on their own.
        //      The results of the RemoteIncrement(0) chain and the RemoteIncrement(4) chain may be intermixed with each other.
        //		The results of the sequence that starts with RemoteIncrement(4) are in strict order.
        // Documentation:
        //		http://msdn.microsoft.com/library/dd781129(VS.100).aspx
        // More information:
        //		http://blogs.msdn.com/pfxteam/archive/2009/11/04/9917581.aspx
        // Other notes:
        //		The combination of Task<T>, ContinueWith() and Unwrap() can be particularly useful for setting up a chain of long-running
        //      tasks where each task uses the results of its predecessor.
        static void Main()
        {
            // Invoking individual tasks is straightforward
            Task<int> t1 = RemoteIncrement(0);
            Console.WriteLine("Started RemoteIncrement(0)");

            // Chain together the results of (simulated) remote operations.
            // The use of Unwrap() instead of .Result below prevents this thread from blocking while setting up this continuation chain.
            Task<int> t2 = RemoteIncrement(4)
                .ContinueWith(t => RemoteIncrement(t.Result))			// RemoteIncrement() returns Task<int> so no unwrapping is needed for the first continuation.
                .Unwrap().ContinueWith(t => RemoteIncrement(t.Result))	// ContinueWith() returns Task<Task<int>>. Therefore unwrapping is needed.
                .Unwrap().ContinueWith(t => RemoteIncrement(t.Result))	// and on it goes...
                .Unwrap();
            Console.WriteLine("Started RemoteIncrement(...(RemoteIncrement(RemoteIncrement(4))...)");

            try
            {
                t1.Wait();
                Console.WriteLine("Finished RemoteIncrement(0)\n");

                t2.Wait();
                Console.WriteLine("Finished RemoteIncrement(...(RemoteIncrement(RemoteIncrement(4))...)");
            }
            catch (AggregateException e)
            {
                Console.WriteLine("A task has thrown the following (unexpected) exception:\n{0}", e);
            }
        }
        // This method represents a remote API.
        static Task<int> RemoteIncrement(int n)
        {
            return Task<int>.Factory.StartNew(
                (obj) =>
                {
                    // Simulate a slow operation
                    Thread.Sleep(1 * 1000);

                    int x = (int)obj;
                    Console.WriteLine("Thread={0}, Next={1}", Thread.CurrentThread.ManagedThreadId, ++x);
                    return x;
                },
                n);
        }
}

Imports System.Threading
Imports System.Threading.Tasks

Module UnwrapDemo
    ' Demonstrated features:
    '   Task.Unwrap()
    '    Task.Factory.StartNew()
    '   Task.ContinueWith()
    ' Expected results:
    ' 	Indicates that continuation chains can be set up virtually instantaneously using Unwrap(), and then left to run on their own.
    '   The results of the RemoteIncrement(0) chain and the RemoteIncrement(4) chain may be intermixed with each other.
    '   The results of the sequence that starts with RemoteIncrement(4) are in strict order.
    ' Documentation:
    '   http://msdn.microsoft.com/library/dd781129(VS.100).aspx
    ' More information:
    '   http://blogs.msdn.com/pfxteam/archive/2009/11/04/9917581.aspx
    ' Other notes:
    '   The combination of Task<T>, ContinueWith() and Unwrap() can be particularly useful for setting up a chain of long-running
    '   tasks where each task uses the results of its predecessor.

    Sub Main()
        ' Invoking individual tasks is straightforward
        Dim t1 As Task(Of Integer) = RemoteIncrement(0)
        Console.WriteLine("Started RemoteIncrement(0)")

        ' Chain together the results of (simulated) remote operations.
        ' The use of Unwrap() instead of .Result below prevents this thread from blocking while setting up this continuation chain.
        ' RemoteIncrement() returns Task<int> so no unwrapping is needed for the first continuation.
        ' ContinueWith() here returns Task<Task<int>>. Therefore unwrapping is needed.
        ' and on it goes...
        Dim t2 As Task(Of Integer) = RemoteIncrement(4).ContinueWith(Function(t) RemoteIncrement(t.Result)).Unwrap().ContinueWith(Function(t) RemoteIncrement(t.Result)).Unwrap().ContinueWith(Function(t) RemoteIncrement(t.Result)).Unwrap()
        Console.WriteLine("Started RemoteIncrement(...(RemoteIncrement(RemoteIncrement(4))...)")

        Try
            t1.Wait()
            Console.WriteLine("Finished RemoteIncrement(0)" & vbLf)

            t2.Wait()
            Console.WriteLine("Finished RemoteIncrement(...(RemoteIncrement(RemoteIncrement(4))...)")
        Catch e As AggregateException
            Console.WriteLine("A task has thrown the following (unexpected) exception:" & vbLf & "{0}", e)

        End Try
    End Sub

    ' This method represents a remote API.
    Function RemoteIncrement(ByVal n As Integer) As Task(Of Integer)
        Return Task(Of Integer).Factory.StartNew(Function(obj)
                                                     ' Simulate a slow operation
                                                     Thread.Sleep(1 * 1000)

                                                     Dim x As Integer = CInt(obj)
                                                     Console.WriteLine("Thread={0}, Next={1}", Thread.CurrentThread.ManagedThreadId, System.Threading.Interlocked.Increment(x))
                                                     Return x
                                                 End Function, n)
    End Function


End Module

Commenti

Spesso è utile essere in grado di restituire un'attività da un Task<TResult>oggetto , in cui l'attività interna rappresenta il lavoro svolto come parte dell'oggetto esterno Task<TResult>. Tuttavia, ciò comporta un Task<Task> comportamento imprevisto (C#) o Task (Of Task) (Visual Basic), che, se non gestito con attenzione, potrebbe produrre un comportamento imprevisto. Unwrap risolve questo problema creando un'attività proxy che rappresenta l'intera operazione asincrona di un'attività di questo tipo.

Vedi anche

• Task Parallel Library (TPL)
• Programmazione asincrona basata su attività
• Procedura: Annullare il wrapping di un'attività annidata

Unwrap<TResult>(Task<Task<TResult>>)

Origine:

TaskExtensions.cs

Crea un oggetto Task proxy che rappresenta l'operazione asincrona di un oggetto Task<Task<T>> (C#) o Task (Of Task(Of T)) (Visual Basic).

public:
generic <typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Threading::Tasks::Task<TResult> ^ Unwrap(System::Threading::Tasks::Task<System::Threading::Tasks::Task<TResult> ^> ^ task);

public static System.Threading.Tasks.Task<TResult> Unwrap<TResult> (this System.Threading.Tasks.Task<System.Threading.Tasks.Task<TResult>> task);

static member Unwrap : System.Threading.Tasks.Task<System.Threading.Tasks.Task<'Result>> -> System.Threading.Tasks.Task<'Result>

<Extension()>
Public Function Unwrap(Of TResult) (task As Task(Of Task(Of TResult))) As Task(Of TResult)

Parametri di tipo

TResult

Tipo di risultato dell'attività.

Parametri

task

Task<Task<TResult>>

Oggetto Task<Task<T>> (C#) o Task (Of Task(Of T)) (Visual Basic) di cui annullare il wrapping.

Restituisce

Task<TResult>

Oggetto Task che rappresenta l'operazione asincrona dell'oggetto Task<Task<T>> (C#) o Task (Of Task(Of T)) (Visual Basic) fornito.

Eccezioni

ArgumentNullException

Eccezione generata se l'argomento task è Null.

Commenti

Spesso è utile essere in grado di restituire un Task oggetto da un Taskoggetto , in cui l'interno Task rappresenta il lavoro svolto come parte dell'oggetto esterno Task. Tuttavia, ciò comporta un Task<Task<T>> comportamento imprevisto (C#) o Task (Of Task(Of T)) (Visual Basic), che, se non gestito con attenzione, potrebbe produrre un comportamento imprevisto. Annulla il wrapping risolve questo problema creando un proxy Task<TResult> che rappresenta l'intera operazione asincrona di tale Task<Task<T>> tipo (C#) o Task (Of Task(Of T)) (Visual Basic).

Vedi anche

• Task Parallel Library (TPL)
• Programmazione asincrona basata su attività
• Procedura: Annullare il wrapping di un'attività annidata