TaskExtensions.Unwrap Methode

Definitie

Naamruimte:
System.Threading.Tasks
Assembly's:
System.Core.dll, System.Threading.Tasks.dll
Assembly's:
netstandard.dll, System.Runtime.dll
Assembly:
System.Threading.Tasks.dll
Assembly:
System.Core.dll
Assembly:
netstandard.dll

Overloads

Name Description
Unwrap(Task<Task>)

Hiermee maakt u een proxy Task die de asynchrone bewerking van een Task<Task> (C#) of Task (Of Task) (Visual Basic) vertegenwoordigt.
Unwrap<TResult>(Task<Task<TResult>>)

Hiermee maakt u een proxy Task die de asynchrone bewerking van een Task<Task<T>> (C#) of Task (Of Task(Of T)) (Visual Basic) vertegenwoordigt.

Unwrap(Task<Task>)

Bron:
TaskExtensions.cs
Bron:
TaskExtensions.cs
Bron:
TaskExtensions.cs
Bron:
TaskExtensions.cs
Bron:
TaskExtensions.cs

Hiermee maakt u een proxy Task die de asynchrone bewerking van een Task<Task> (C#) of Task (Of Task) (Visual Basic) vertegenwoordigt.

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

Parameters

task
Task<Task>

De Task<Task> (C#) of Task (Of Task) (Visual Basic) om uitpakken uit te pakken.

Retouren

Task

Een taak die de asynchrone bewerking van de opgegeven System.Threading.Tasks.Task(Of Task)taak vertegenwoordigt.

Uitzonderingen

ArgumentNullException

De uitzondering die wordt gegenereerd als het task argument null is.

Voorbeelden

In het volgende voorbeeld ziet u hoe u een taak uitpakt:

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

Opmerkingen

Het is vaak handig om een taak te retourneren van een Task<TResult>, waarbij de binnenste taak werk vertegenwoordigt dat wordt uitgevoerd als onderdeel van de buitenste Task<TResult>. Als u dit doet, resulteert dit echter in een Task<Task> (C#) of Task (Of Task) (Visual Basic), wat, indien niet zorgvuldig behandeld, onverwacht gedrag kan opleveren. Los dit probleem op door een proxytaak te maken die de hele asynchrone bewerking van een dergelijke taak vertegenwoordigt.

Zie ook

Van toepassing op

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

Bron:
TaskExtensions.cs
Bron:
TaskExtensions.cs
Bron:
TaskExtensions.cs
Bron:
TaskExtensions.cs
Bron:
TaskExtensions.cs

Hiermee maakt u een proxy Task die de asynchrone bewerking van een Task<Task<T>> (C#) of Task (Of Task(Of T)) (Visual Basic) vertegenwoordigt.

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)

Type parameters

TResult

Het type resultaat van de taak.

Parameters

task
Task<Task<TResult>>

De Task<Task<T>> (C#) of Task (Of Task(Of T)) (Visual Basic) om uitpakken uit te pakken.

Retouren

Task<TResult>

Een Task die de asynchrone bewerking van de opgegeven Task<Task<T>> (C#) of Task (Of Task(Of T)) (Visual Basic) vertegenwoordigt.

Uitzonderingen

ArgumentNullException

De uitzondering die wordt gegenereerd als het task argument null is.

Opmerkingen

Het is vaak handig om een van een TaskTask, waarbij het binnenste Task werk vertegenwoordigt als onderdeel van het buitenste Task. Als u dit doet, resulteert dit echter in een Task<Task<T>> (C#) of Task (Of Task(Of T)) (Visual Basic), wat, indien niet zorgvuldig behandeld, onverwacht gedrag kan opleveren. Los dit probleem op door een proxy Task<TResult> te maken die de hele asynchrone bewerking van een dergelijke Task<Task<T>> (C#) of Task (Of Task(Of T)) (Visual Basic) vertegenwoordigt.

Zie ook

Van toepassing op