ManagementEventWatcher.WaitForNextEvent ManagementEventWatcher.WaitForNextEvent ManagementEventWatcher.WaitForNextEvent ManagementEventWatcher.WaitForNextEvent Method

Definizione

Attende l'evento successivo che corrisponde alla query specificata in arrivo, quindi lo restituisce.Waits for the next event that matches the specified query to arrive, and then returns it.

public:
 System::Management::ManagementBaseObject ^ WaitForNextEvent();
public System.Management.ManagementBaseObject WaitForNextEvent ();
member this.WaitForNextEvent : unit -> System.Management.ManagementBaseObject
Public Function WaitForNextEvent () As ManagementBaseObject

Restituisce

ManagementBaseObject che rappresenta il nuovo oggetto in arrivo.A ManagementBaseObject representing the newly arrived event.

Esempi

Nell'esempio seguente viene illustrato il client riceve una notifica quando un'istanza del Win32_Process viene creato perché è la classe di evento InstanceCreationEvent.The following example shows how the client receives notification when an instance of Win32_Process is created because the event class is __InstanceCreationEvent. Per altre informazioni, vedere la Windows Management Instrumentation documentazione.For more information, see the Windows Management Instrumentation documentation. Il client riceve gli eventi in modo sincrono chiamando il metodo WaitForNextEvent.The client receives events synchronously by calling the WaitForNextEvent method. Questo esempio può essere testato avviando un processo, ad esempio Blocco note, mentre il codice di esempio è in esecuzione.This example can be tested by starting a process, such as Notepad, while the example code is running.

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
        WqlEventQuery query = 
            new WqlEventQuery("__InstanceCreationEvent", 
            new TimeSpan(0,0,1), 
            "TargetInstance isa \"Win32_Process\"");

        // Initialize an event watcher and subscribe to events 
        // that match this query
        ManagementEventWatcher watcher =
            new ManagementEventWatcher();
        watcher.Query = 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;
    }
}
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 WqlEventQuery( _
            "__InstanceCreationEvent", _
            New TimeSpan(0, 0, 1), _
            "TargetInstance isa ""Win32_Process""")

        ' Initialize an event watcher and subscribe to events 
        ' that match this query
        Dim watcher As New ManagementEventWatcher
        watcher.Query = query
        ' times 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.")
        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

Commenti

Se l'oggetto evento di controllo contiene le opzioni con un timeout specificato, l'API attenderà l'evento successivo solo per il periodo di tempo; specificato in caso contrario, l'API verrà bloccata finché non si verifica l'evento successivo.If the event watcher object contains options with a specified time-out, the API will wait for the next event only for the specified amount of time; otherwise, the API will be blocked until the next event occurs.

Sicurezza di .NET Framework.NET Framework Security

Attendibilità totale per il chiamante immediato.Full trust for the immediate caller. Impossibile usare questo membro in codice parzialmente attendibile.This member cannot be used by partially trusted code. Per altre informazioni, vedere utilizzo di librerie da codice parzialmente attendibile.For more information, see Using Libraries from Partially Trusted Code.

Si applica a