AsyncLocal<T> AsyncLocal<T> AsyncLocal<T> AsyncLocal<T> Class

Définition

Représente les données ambiantes qui sont locales à un flux de contrôle asynchrone donné, par exemple une méthode asynchrone.Represents ambient data that is local to a given asynchronous control flow, such as an asynchronous method.

generic <typename T>
public ref class AsyncLocal sealed
public sealed class AsyncLocal<T>
type AsyncLocal<'T> = class
Public NotInheritable Class AsyncLocal(Of T)

Paramètres de type

T

Type des données ambiantes.The type of the ambient data.

Héritage
AsyncLocal<T>AsyncLocal<T>AsyncLocal<T>AsyncLocal<T>

Exemples

L’exemple suivant utilise la AsyncLocal<T> classe pour conserver une valeur de chaîne dans un flux asynchrone.The following example uses the AsyncLocal<T> class to persist a string value across an asynchronous flow. Il compare également l’utilisation de AsyncLocal<T> avec ThreadLocal<T>.It also contrasts the use of AsyncLocal<T> with ThreadLocal<T>.

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

class Example
{
    static AsyncLocal<string> _asyncLocalString = new AsyncLocal<string>();

    static ThreadLocal<string> _threadLocalString = new ThreadLocal<string>();

    static async Task AsyncMethodA()
    {
        // Start multiple async method calls, with different AsyncLocal values.
        // We also set ThreadLocal values, to demonstrate how the two mechanisms differ.
        _asyncLocalString.Value = "Value 1";
        _threadLocalString.Value = "Value 1";
        var t1 = AsyncMethodB("Value 1");

        _asyncLocalString.Value = "Value 2";
        _threadLocalString.Value = "Value 2";
        var t2 = AsyncMethodB("Value 2");

        // Await both calls
        await t1;
        await t2;
     }

    static async Task AsyncMethodB(string expectedValue)
    {
        Console.WriteLine("Entering AsyncMethodB.");
        Console.WriteLine("   Expected '{0}', AsyncLocal value is '{1}', ThreadLocal value is '{2}'", 
                          expectedValue, _asyncLocalString.Value, _threadLocalString.Value);
        await Task.Delay(100);
        Console.WriteLine("Exiting AsyncMethodB.");
        Console.WriteLine("   Expected '{0}', got '{1}', ThreadLocal value is '{2}'", 
                          expectedValue, _asyncLocalString.Value, _threadLocalString.Value);
    }

    static async Task Main(string[] args)
    {
        await AsyncMethodA();
    }
}
// The example displays the following output:
//   Entering AsyncMethodB.
//      Expected 'Value 1', AsyncLocal value is 'Value 1', ThreadLocal value is 'Value 1'
//   Entering AsyncMethodB.
//      Expected 'Value 2', AsyncLocal value is 'Value 2', ThreadLocal value is 'Value 2'
//   Exiting AsyncMethodB.
//      Expected 'Value 2', got 'Value 2', ThreadLocal value is ''
//   Exiting AsyncMethodB.
//      Expected 'Value 1', got 'Value 1', ThreadLocal value is ''
Imports System.Threading
Imports System.Threading.Tasks

Module Example
    Dim _asyncLocalString As New AsyncLocal(Of String)()

    Dim _threadLocalString As New ThreadLocal(Of String)()

    Async Function AsyncMethodA() As Task
        ' Start multiple async method calls, with different AsyncLocal values.
        ' We also set ThreadLocal values, to demonstrate how the two mechanisms differ.
        _asyncLocalString.Value = "Value 1"
        _threadLocalString.Value = "Value 1"
        Dim t1 = AsyncMethodB("Value 1")

        _asyncLocalString.Value = "Value 2"
        _threadLocalString.Value = "Value 2"
        Dim t2 = AsyncMethodB("Value 2")

        ' Await both calls
        await t1
        await t2
     End Function

    Async Function AsyncMethodB(expectedValue As String) As Task
        Console.WriteLine("Entering AsyncMethodB.")
        Console.WriteLine("   Expected '{0}', AsyncLocal value is '{1}', ThreadLocal value is '{2}'", 
                          expectedValue, _asyncLocalString.Value, _threadLocalString.Value)
        await Task.Delay(100)
        Console.WriteLine("Exiting AsyncMethodB.")
        Console.WriteLine("   Expected '{0}', got '{1}', ThreadLocal value is '{2}'", 
                          expectedValue, _asyncLocalString.Value, _threadLocalString.Value)
    End Function

   Public Sub Main()
       AsyncMethodA.Wait()
   End Sub
End Module
' The example displays the following output:
'   Entering AsyncMethodB.
'      Expected 'Value 1', AsyncLocal value is 'Value 1', ThreadLocal value is 'Value 1'
'   Entering AsyncMethodB.
'      Expected 'Value 2', AsyncLocal value is 'Value 2', ThreadLocal value is 'Value 2'
'   Exiting AsyncMethodB.
'      Expected 'Value 2', got 'Value 2', ThreadLocal value is ''
'   Exiting AsyncMethodB.
'      Expected 'Value 1', got 'Value 1', ThreadLocal value is ''

Remarques

Étant donné que le modèle de programmation asynchrone basé sur des tâches tend à extraire de l’utilisation de threads, AsyncLocal<T> instances peuvent être utilisées pour conserver les données entre plusieurs threads.Because the task-based asynchronous programming model tends to abstract the use of threads, AsyncLocal<T> instances can be used to persist data across threads.

Le AsyncLocal<T> classe fournit également des notifications facultatives lorsque la valeur associée soit les modifications du thread actuel, car il a été modifiée explicitement en définissant le Value propriété, ou modifié implicitement lorsque le thread a rencontré un await ou autres transition de contexte.The AsyncLocal<T> class also provides optional notifications when the value associated with the current thread changes, either because it was explicitly changed by setting the Value property, or implicitly changed when the thread encountered an await or other context transition.

Constructeurs

AsyncLocal<T>() AsyncLocal<T>() AsyncLocal<T>() AsyncLocal<T>()

Instancie une instance de AsyncLocal<T> qui ne reçoit pas de notifications de modification.Instantiates an AsyncLocal<T> instance that does not receive change notifications.

AsyncLocal<T>(Action<AsyncLocalValueChangedArgs<T>>) AsyncLocal<T>(Action<AsyncLocalValueChangedArgs<T>>) AsyncLocal<T>(Action<AsyncLocalValueChangedArgs<T>>) AsyncLocal<T>(Action<AsyncLocalValueChangedArgs<T>>)

Instancie une instance locale de AsyncLocal<T> qui ne reçoit pas de notifications de modification.Instantiates an AsyncLocal<T> local instance that receives change notifications.

Propriétés

Value Value Value Value

Obtient ou définit la valeur des données ambiantes.Gets or sets the value of the ambient data.

Méthodes

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Détermine si l'objet spécifié est identique à l'objet actuel.Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Fait office de fonction de hachage par défaut.Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

Obtient le Type de l'instance actuelle.Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Crée une copie superficielle du Object actuel.Creates a shallow copy of the current Object.

(Inherited from Object)
ToString() ToString() ToString() ToString()

Retourne une chaîne qui représente l'objet actuel.Returns a string that represents the current object.

(Inherited from Object)

S’applique à