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Installez le package NuGet Microsoft.Data.SqlClient pour utiliser ces exemples. Microsoft.Data.SqlClient prend en charge les méthodes BeginExecute et EndExecute présentées ici sans option de chaîne de connexion asynchrone. N'ajoutez pas Asynchronous Processing=true; Microsoft.Data.SqlClient ne prend pas en charge ce mot clé. Pour le nouveau code, préférez ExecuteReaderAsync et ExecuteNonQueryAsync avec await, et utilisez Task.WhenAny ou Task.WhenAll pour coordonner les opérations sans bloquer un thread de requête.
Les modèles de rappel et d’interrogation pour la gestion des opérations asynchrones sont utiles lorsque votre application ne traite qu’une seule opération asynchrone à la fois. Les modèles d’attente offrent un moyen plus flexible de traiter plusieurs opérations asynchrones. Il existe deux modèles d'attente nommés pour les méthodes WaitHandle utilisées pour leur implémentation : le modèle d’attente (Chacun) et le modèle d’attente (Tous).
Pour utiliser l’un ou l’autre des modèles Wait, utilisez la propriété AsyncWaitHandle de l’objet IAsyncResult retourné par les méthodes BeginExecuteXmlReader, BeginExecuteReader ou BeginExecuteNonQuery. Passez un tableau de WaitHandle objets à WaitAny ou WaitAll.
Les deux méthodes d’attente surveillent les opérations asynchrones, jusqu'à leur complétion. La méthode WaitAny attend que l’une des opérations soit terminée ou expire. Une fois que vous savez qu’une opération particulière est terminée, vous pouvez traiter ses résultats, puis continuer à attendre que l’opération suivante se termine ou expire. La méthode WaitAll attend que tous les processus du tableau d’instances WaitHandle se terminent ou expirent avant de continuer.
L’avantage des modèles d’attente est plus important lorsque vous devez exécuter plusieurs opérations de longue durée sur des serveurs différents ou lorsque votre serveur est suffisamment puissant pour traiter toutes les requêtes en même temps. Dans les exemples présentés ici, trois requêtes émulent de longs processus en ajoutant des commandes WAITFOR de longueurs variables aux requêtes SELECT sans importance.
Exemple : Modèle d'attente (quelconque)
L’exemple suivant illustre le modèle d’attente (N’importe lequel). Une fois qu’il a démarré trois opérations asynchrones, le code appelle WaitAny pour attendre la fin de toute opération. Pour chaque opération terminée, le code appelle EndExecuteReader et lit le résultat SqlDataReader. Une application peut utiliser ces résultats pour remplir une partie de la page. L’exemple ajoute plutôt le temps d’achèvement à la zone de texte correspondante. Chaque enregistrement indique le moment où le code traite une opération terminée.
Étant donné que les handles terminés restent signalés, l’exemple supprime chaque opération terminée des listes en attente avant d’attendre à nouveau.
Pour configurer cet exemple, créez un nouveau projet de site Web ASP.NET. Placez un contrôle Button et quatre contrôles TextBox sur la page (en acceptant le nom par défaut pour chaque contrôle).
Ajoutez le code suivant à la classe du formulaire. Dans les deux exemples de modèle Wait, remplacez les points de suspension retournés par GetConnectionString par votre chaîne de connexion. Pour un serveur distant avec l’authentification intégrée Windows, utilisez Server=<server>;Database=<database>;Integrated Security=true;Encrypt=true. Remplacez <database> et <server> par les noms de votre serveur et de votre base de données, puis configurez un certificat de serveur approuvé par le client. Pour obtenir d’autres options d’authentification, consultez la syntaxe de chaîne de connexion.
' Add these to the top of the class
Imports System
Imports System.Collections.Generic
Imports System.Data
Imports Microsoft.Data.SqlClient
Imports System.Threading
' Add this code to the page's class:
Private Function GetConnectionString() As String
' To avoid storing the connection string in your code,
' you can retrieve it from a configuration file.
Return "..."
End Function
Sub Button1_Click( _
ByVal sender As Object, ByVal e As System.EventArgs)
' In a real-world application, you might be connecting to
' three different servers or databases. For the example,
' we connect to only one.
Dim connection1 As New SqlConnection(GetConnectionString())
Dim connection2 As New SqlConnection(GetConnectionString())
Dim connection3 As New SqlConnection(GetConnectionString())
' To keep the example simple, all three asynchronous
' processes select a row from the same table. WAITFOR
' commands are used to emulate long-running processes
' that complete after different periods of time.
Dim commandText1 As String = _
"WAITFOR DELAY '0:0:01';" & _
"SELECT * FROM Production.Product " & _
"WHERE ProductNumber = 'BL-2036'"
Dim commandText2 As String = _
"WAITFOR DELAY '0:0:05';" & _
"SELECT * FROM Production.Product " & _
"WHERE ProductNumber = 'BL-2036'"
Dim commandText3 As String = _
"WAITFOR DELAY '0:0:10';" & _
"SELECT * FROM Production.Product " & _
"WHERE ProductNumber = 'BL-2036'"
Dim waitHandles As New List(Of WaitHandle)
Dim pending As New List(Of Integer) From {0, 1, 2}
Try
' For each process, open a connection and begin execution.
' Use the IAsyncResult object returned by
' BeginExecuteReader to add a WaitHandle for the process
' to the pending list.
connection1.Open()
Dim command1 As New SqlCommand(commandText1, connection1)
Dim result1 As IAsyncResult = _
command1.BeginExecuteReader()
waitHandles.Add(result1.AsyncWaitHandle)
connection2.Open()
Dim command2 As New SqlCommand(commandText2, connection2)
Dim result2 As IAsyncResult = _
command2.BeginExecuteReader()
waitHandles.Add(result2.AsyncWaitHandle)
connection3.Open()
Dim command3 As New SqlCommand(commandText3, connection3)
Dim result3 As IAsyncResult = _
command3.BeginExecuteReader()
waitHandles.Add(result3.AsyncWaitHandle)
Dim index As Integer
For countWaits As Integer = 1 To 3
' WaitAny waits for any of the processes to complete.
' The return value is either the index of the
' array element whose process just completed, or
' the WaitTimeout value.
index = WaitHandle.WaitAny(waitHandles.ToArray(), 60000, False)
If index = WaitHandle.WaitTimeout Then
Throw New Exception("Timeout")
End If
' This example doesn't actually do anything with the
' data returned by the processes, but the code opens
' readers for each just to demonstrate the concept.
' Instead of using the returned data to fill the
' controls on the page, the example adds the time
' the process was completed to the corresponding
' text box.
Select Case pending(index)
Case 0
Dim reader1 As SqlDataReader
reader1 = command1.EndExecuteReader(result1)
If reader1.Read Then
TextBox1.Text = _
"Completed " & _
System.DateTime.Now.ToLongTimeString()
End If
reader1.Close()
Case 1
Dim reader2 As SqlDataReader
reader2 = command2.EndExecuteReader(result2)
If reader2.Read Then
TextBox2.Text = _
"Completed " & _
System.DateTime.Now.ToLongTimeString()
End If
reader2.Close()
Case 2
Dim reader3 As SqlDataReader
reader3 = command3.EndExecuteReader(result3)
If reader3.Read Then
TextBox3.Text = _
"Completed " & _
System.DateTime.Now.ToLongTimeString()
End If
reader3.Close()
End Select
waitHandles.RemoveAt(index)
pending.RemoveAt(index)
Next
Catch ex As Exception
TextBox4.Text = ex.ToString
End Try
connection1.Close()
connection2.Close()
connection3.Close()
End Sub
// Add the following using directives, if they aren't already there.
using System;
using System.Collections.Generic;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Threading;
using Microsoft.Data.SqlClient;
// Add this code to the page's class
string GetConnectionString()
// To avoid storing the connection string in your code,
// you can retrieve it from a configuration file.
{
return "...";
}
void Button1_Click(object sender, System.EventArgs e)
{
// In a real-world application, you might be connecting to
// three different servers or databases. For the example,
// we connect to only one.
SqlConnection connection1 =
new SqlConnection(GetConnectionString());
SqlConnection connection2 =
new SqlConnection(GetConnectionString());
SqlConnection connection3 =
new SqlConnection(GetConnectionString());
// To keep the example simple, all three asynchronous
// processes select a row from the same table. WAITFOR
// commands are used to emulate long-running processes
// that complete after different periods of time.
string commandText1 = "WAITFOR DELAY '0:0:01';" +
"SELECT * FROM Production.Product " +
"WHERE ProductNumber = 'BL-2036'";
string commandText2 = "WAITFOR DELAY '0:0:05';" +
"SELECT * FROM Production.Product " +
"WHERE ProductNumber = 'BL-2036'";
string commandText3 = "WAITFOR DELAY '0:0:10';" +
"SELECT * FROM Production.Product " +
"WHERE ProductNumber = 'BL-2036'";
try
// For each process, open a connection and begin
// execution. Use the IAsyncResult object returned by
// BeginExecuteReader to add a WaitHandle for the
// process to the pending list.
{
connection1.Open();
SqlCommand command1 =
new SqlCommand(commandText1, connection1);
IAsyncResult result1 = command1.BeginExecuteReader();
WaitHandle waitHandle1 = result1.AsyncWaitHandle;
connection2.Open();
SqlCommand command2 =
new SqlCommand(commandText2, connection2);
IAsyncResult result2 = command2.BeginExecuteReader();
WaitHandle waitHandle2 = result2.AsyncWaitHandle;
connection3.Open();
SqlCommand command3 =
new SqlCommand(commandText3, connection3);
IAsyncResult result3 = command3.BeginExecuteReader();
WaitHandle waitHandle3 = result3.AsyncWaitHandle;
List<WaitHandle> waitHandles = new List<WaitHandle> {
waitHandle1, waitHandle2, waitHandle3
};
List<int> pending = new List<int> { 0, 1, 2 };
int index;
for (int countWaits = 0; countWaits <= 2; countWaits++)
{
// WaitAny waits for any of the processes to
// complete. The return value is either the index
// of the array element whose process just
// completed, or the WaitTimeout value.
index = WaitHandle.WaitAny(waitHandles.ToArray(),
60000, false);
if (index == WaitHandle.WaitTimeout)
{
throw new Exception("Timeout");
}
// This example doesn't actually do anything with
// the data returned by the processes, but the
// code opens readers for each just to demonstrate
// the concept.
// Instead of using the returned data to fill the
// controls on the page, the example adds the time
// the process was completed to the corresponding
// text box.
switch (pending[index])
{
case 0:
SqlDataReader reader1;
reader1 =
command1.EndExecuteReader(result1);
if (reader1.Read())
{
TextBox1.Text =
"Completed " +
System.DateTime.Now.ToLongTimeString();
}
reader1.Close();
break;
case 1:
SqlDataReader reader2;
reader2 =
command2.EndExecuteReader(result2);
if (reader2.Read())
{
TextBox2.Text =
"Completed " +
System.DateTime.Now.ToLongTimeString();
}
reader2.Close();
break;
case 2:
SqlDataReader reader3;
reader3 =
command3.EndExecuteReader(result3);
if (reader3.Read())
{
TextBox3.Text =
"Completed " +
System.DateTime.Now.ToLongTimeString();
}
reader3.Close();
break;
}
waitHandles.RemoveAt(index);
pending.RemoveAt(index);
}
}
catch (Exception ex)
{
TextBox4.Text = ex.ToString();
}
connection1.Close();
connection2.Close();
connection3.Close();
}
Exemple : Modèle d'attente (Tous)
L’exemple suivant illustre le modèle Wait (Tous). Après le démarrage de trois processus asynchrones, la méthode WaitAll est appelée pour attendre l’achèvement ou l’expiration des processus.
Comme dans cet exemple de modèle d’attente (N’importe lequel), l’heure de fin du processus est ajoutée à une zone de texte correspondant au processus. Là encore, ces heures dans les zones de texte illustrent le point suivant : d'après la méthode WaitAny, le code est exécuté uniquement après l'achèvement de tous les processus.
Pour configurer cet exemple, créez un nouveau projet de site Web ASP.NET. Placez un contrôle Button et quatre contrôles TextBox sur la page (en acceptant le nom par défaut pour chaque contrôle).
Ajoutez le code suivant à la classe du formulaire, en modifiant la chaîne de connexion en fonction des besoins de votre environnement.
' Add these to the top of the class
Imports System
Imports System.Data
Imports Microsoft.Data.SqlClient
Imports System.Threading
' Add this code to the page's class:
Private Function GetConnectionString() As String
' To avoid storing the connection string in your code,
' you can retrieve it from a configuration file.
Return "..."
End Function
Sub Button1_Click( _
ByVal sender As Object, ByVal e As System.EventArgs)
' In a real-world application, you might be connecting to
' three different servers or databases. For the example,
' we connect to only one.
Dim connection1 As New SqlConnection(GetConnectionString())
Dim connection2 As New SqlConnection(GetConnectionString())
Dim connection3 As New SqlConnection(GetConnectionString())
' To keep the example simple, all three asynchronous
' processes select a row from the same table. WAITFOR
' commands are used to emulate long-running processes
' that complete after different periods of time.
Dim commandText1 As String = _
"UPDATE Production.Product " & _
"SET ReorderPoint = ReorderPoint + 1 " & _
"WHERE ReorderPoint Is Not Null;" & _
"WAITFOR DELAY '0:0:01';" & _
"UPDATE Production.Product " & _
"SET ReorderPoint = ReorderPoint - 1 " & _
"WHERE ReorderPoint Is Not Null"
Dim commandText2 As String = _
"UPDATE Production.Product " & _
"SET ReorderPoint = ReorderPoint + 1 " & _
"WHERE ReorderPoint Is Not Null;" & _
"WAITFOR DELAY '0:0:05';" & _
"UPDATE Production.Product " & _
"SET ReorderPoint = ReorderPoint - 1 " & _
"WHERE ReorderPoint Is Not Null"
Dim commandText3 As String = _
"UPDATE Production.Product " & _
"SET ReorderPoint = ReorderPoint + 1 " & _
"WHERE ReorderPoint Is Not Null;" & _
"WAITFOR DELAY '0:0:10';" & _
"UPDATE Production.Product " & _
"SET ReorderPoint = ReorderPoint - 1 " & _
"WHERE ReorderPoint Is Not Null"
Dim waitHandles(2) As WaitHandle
Try
' For each process, open a connection and begin execution.
' Use the IAsyncResult object returned by
' BeginExecuteReader to add a WaitHandle for the process
' to the array.
connection1.Open()
Dim command1 As New SqlCommand(commandText1, connection1)
Dim result1 As IAsyncResult = _
command1.BeginExecuteNonQuery()
waitHandles(0) = result1.AsyncWaitHandle
connection2.Open()
Dim command2 As New SqlCommand(commandText2, connection2)
Dim result2 As IAsyncResult = _
command2.BeginExecuteNonQuery()
waitHandles(1) = result2.AsyncWaitHandle
connection3.Open()
Dim command3 As New SqlCommand(commandText3, connection3)
Dim result3 As IAsyncResult = _
command3.BeginExecuteNonQuery()
waitHandles(2) = result3.AsyncWaitHandle
' WaitAll waits for all of the processes to complete.
' The return value is True if all processes completed,
' False if any process timed out.
Dim result As Boolean = _
WaitHandle.WaitAll(waitHandles, 60000, False)
If result Then
Dim rowCount1 As Long = _
command1.EndExecuteNonQuery(result1)
TextBox1.Text = _
"Completed " & _
System.DateTime.Now.ToLongTimeString()
Dim rowCount2 As Long = _
command2.EndExecuteNonQuery(result2)
TextBox2.Text = _
"Completed " & _
System.DateTime.Now.ToLongTimeString()
Dim rowCount3 As Long = _
command3.EndExecuteNonQuery(result3)
TextBox3.Text = _
"Completed " & _
System.DateTime.Now.ToLongTimeString()
Else
Throw New Exception("Timeout")
End If
Catch ex As Exception
TextBox4.Text = ex.ToString
End Try
connection1.Close()
connection2.Close()
connection3.Close()
End Sub
// Add the following using directives, if they aren't already there.
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Threading;
using Microsoft.Data.SqlClient;
// Add this code to the page's class
string GetConnectionString()
// To avoid storing the connection string in your code,
// you can retrieve it from a configuration file.
{
return "...";
}
void Button1_Click(object sender, System.EventArgs e)
{
// In a real-world application, you might be connecting to
// three different servers or databases. For the example,
// we connect to only one.
SqlConnection connection1 =
new SqlConnection(GetConnectionString());
SqlConnection connection2 =
new SqlConnection(GetConnectionString());
SqlConnection connection3 =
new SqlConnection(GetConnectionString());
// To keep the example simple, all three asynchronous
// processes execute UPDATE queries that result in
// no change to the data. WAITFOR
// commands are used to emulate long-running processes
// that complete after different periods of time.
string commandText1 =
"UPDATE Production.Product " +
"SET ReorderPoint = ReorderPoint + 1 " +
"WHERE ReorderPoint Is Not Null;" +
"WAITFOR DELAY '0:0:01';" +
"UPDATE Production.Product " +
"SET ReorderPoint = ReorderPoint - 1 " +
"WHERE ReorderPoint Is Not Null";
string commandText2 =
"UPDATE Production.Product " +
"SET ReorderPoint = ReorderPoint + 1 " +
"WHERE ReorderPoint Is Not Null;" +
"WAITFOR DELAY '0:0:05';" +
"UPDATE Production.Product " +
"SET ReorderPoint = ReorderPoint - 1 " +
"WHERE ReorderPoint Is Not Null";
string commandText3 =
"UPDATE Production.Product " +
"SET ReorderPoint = ReorderPoint + 1 " +
"WHERE ReorderPoint Is Not Null;" +
"WAITFOR DELAY '0:0:10';" +
"UPDATE Production.Product " +
"SET ReorderPoint = ReorderPoint - 1 " +
"WHERE ReorderPoint Is Not Null";
try
// For each process, open a connection and begin
// execution. Use the IAsyncResult object returned by
// BeginExecuteReader to add a WaitHandle for the
// process to the array.
{
connection1.Open();
SqlCommand command1 =
new SqlCommand(commandText1, connection1);
IAsyncResult result1 = command1.BeginExecuteNonQuery();
WaitHandle waitHandle1 = result1.AsyncWaitHandle;
connection2.Open();
SqlCommand command2 =
new SqlCommand(commandText2, connection2);
IAsyncResult result2 = command2.BeginExecuteNonQuery();
WaitHandle waitHandle2 = result2.AsyncWaitHandle;
connection3.Open();
SqlCommand command3 =
new SqlCommand(commandText3, connection3);
IAsyncResult result3 = command3.BeginExecuteNonQuery();
WaitHandle waitHandle3 = result3.AsyncWaitHandle;
WaitHandle[] waitHandles = {
waitHandle1, waitHandle2, waitHandle3
};
bool result;
// WaitAll waits for all of the processes to
// complete. The return value is True if the processes
// all completed successfully, False if any process
// timed out.
result = WaitHandle.WaitAll(waitHandles, 60000, false);
if(result)
{
long rowCount1 =
command1.EndExecuteNonQuery(result1);
TextBox1.Text = "Completed " +
System.DateTime.Now.ToLongTimeString();
long rowCount2 =
command2.EndExecuteNonQuery(result2);
TextBox2.Text = "Completed " +
System.DateTime.Now.ToLongTimeString();
long rowCount3 =
command3.EndExecuteNonQuery(result3);
TextBox3.Text = "Completed " +
System.DateTime.Now.ToLongTimeString();
}
else
{
throw new Exception("Timeout");
}
}
catch (Exception ex)
{
TextBox4.Text = ex.ToString();
}
connection1.Close();
connection2.Close();
connection3.Close();
}