ManagementEventWatcher.WaitForNextEvent Metode

Definisi

Ruang nama:

System.Management

Rakitan:

System.Management.dll

Paket:

System.Management v8.0.0

Sumber:

ManagementEventWatcher.cs

Menunggu peristiwa berikutnya yang cocok dengan kueri yang ditentukan tiba, lalu mengembalikannya.

public:
 System::Management::ManagementBaseObject ^ WaitForNextEvent();

public System.Management.ManagementBaseObject WaitForNextEvent ();

member this.WaitForNextEvent : unit -> System.Management.ManagementBaseObject

Public Function WaitForNextEvent () As ManagementBaseObject

Mengembalikan

ManagementBaseObject

mewakili ManagementBaseObject peristiwa yang baru tiba.

Contoh

Contoh berikut menunjukkan bagaimana klien menerima pemberitahuan saat instans Win32_Process dibuat karena kelas peristiwa __InstanceCreationEvent. Untuk informasi selengkapnya, lihat dokumentasi Instrumentasi Manajemen Windows . Klien menerima peristiwa secara sinkron dengan memanggil WaitForNextEvent metode . Contoh ini dapat diuji dengan memulai proses, seperti Notepad, saat kode contoh sedang berjalan.

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.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

Keterangan

Jika objek pengamat peristiwa berisi opsi dengan waktu habis yang ditentukan, API akan menunggu peristiwa berikutnya hanya untuk jumlah waktu yang ditentukan; jika tidak, API akan diblokir hingga peristiwa berikutnya terjadi.

.NET Framework Security

Kepercayaan penuh untuk penelepon segera. Anggota ini tidak dapat digunakan oleh kode tepercaya sebagian. Untuk informasi selengkapnya, lihat Menggunakan Pustaka dari Kode Tepercaya Sebagian.