EventQuery-Klasse
Stellt eine WMI-Ereignisabfrage dar.
Namespace: System.Management
Assembly: System.Management (in system.management.dll)
Syntax
'Declaration
Public Class EventQuery
Inherits ManagementQuery
'Usage
Dim instance As EventQuery
public class EventQuery : ManagementQuery
public ref class EventQuery : public ManagementQuery
public class EventQuery extends ManagementQuery
public class EventQuery extends ManagementQuery
Beispiel
Im folgenden Beispiel wird veranschaulicht, wie der Client eine Benachrichtigung empfängt, wenn eine Instanz von Win32_Process erstellt wird, da die Ereignisklasse __InstanceCreationEvent ist. Weitere Informationen über die Windows-Verwaltungsinstrumentation finden Sie in der Dokumentation zur Windows-Verwaltungsinstrumentation in der MSDN Library unter https://msdn.microsoft.com/library/deu. Der Client empfängt Ereignisse synchron durch Aufrufen der WaitForNextEvent-Methode. Während der Beispielcode ausgeführt wird, kann dieses Beispiel durch Starten eines Prozesses wie Editor getestet werden.
Imports System
Imports System.Management
' This example shows synchronous consumption of events.
' The client is blocked while waiting for events.
Public Class EventWatcherPolling
Public Overloads Shared Function _
Main(ByVal args() As String) As Integer
' Create event query to be notified within 1 second of
' a change in a service
Dim query As New EventQuery
query.QueryString = "SELECT * FROM" & _
" __InstanceCreationEvent WITHIN 1 " & _
"WHERE TargetInstance isa ""Win32_Process"""
' Initialize an event watcher and subscribe to events
' that match this query
Dim watcher As New ManagementEventWatcher(query)
' times watcher.WaitForNextEvent in 5 seconds
watcher.Options.Timeout = New TimeSpan(0, 0, 50)
' Block until the next event occurs
' Note: this can be done in a loop
' if waiting for more than one occurrence
Console.WriteLine( _
"Open an application (notepad.exe) to trigger an event.")
Dim e As ManagementBaseObject = _
watcher.WaitForNextEvent()
'Display information from the event
Console.WriteLine( _
"Process {0} has created, path is: {1}", _
CType(e("TargetInstance"), _
ManagementBaseObject)("Name"), _
CType(e("TargetInstance"), _
ManagementBaseObject)("ExecutablePath"))
'Cancel the subscription
watcher.Stop()
Return 0
End Function 'Main
End Class 'EventWatcherPolling
using System;
using System.Management;
// This example shows synchronous consumption of events.
// The client is blocked while waiting for events.
public class EventWatcherPolling
{
public static int Main(string[] args)
{
// Create event query to be notified within 1 second of
// a change in a service
EventQuery query = new EventQuery();
query.QueryString = "SELECT * FROM" +
" __InstanceCreationEvent WITHIN 1 " +
"WHERE TargetInstance isa \"Win32_Process\"";
// Initialize an event watcher and subscribe to events
// that match this query
ManagementEventWatcher watcher =
new ManagementEventWatcher(query);
// times out watcher.WaitForNextEvent in 5 seconds
watcher.Options.Timeout = new TimeSpan(0,0,5);
// Block until the next event occurs
// Note: this can be done in a loop if waiting for
// more than one occurrence
Console.WriteLine(
"Open an application (notepad.exe) to trigger an event.");
ManagementBaseObject e = watcher.WaitForNextEvent();
//Display information from the event
Console.WriteLine(
"Process {0} has been created, path is: {1}",
((ManagementBaseObject)e
["TargetInstance"])["Name"],
((ManagementBaseObject)e
["TargetInstance"])["ExecutablePath"]);
//Cancel the subscription
watcher.Stop();
return 0;
}
}
Vererbungshierarchie
System.Object
System.Management.ManagementQuery
System.Management.EventQuery
System.Management.WqlEventQuery
Threadsicherheit
Alle öffentlichen statischen (Shared in Visual Basic) Member dieses Typs sind threadsicher. Bei Instanzmembern ist die Threadsicherheit nicht gewährleistet.
Plattformen
Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.
Versionsinformationen
.NET Framework
Unterstützt in: 2.0, 1.1, 1.0