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ManagementEventWatcher.WaitForNextEvent Method

Waits for the next event that matches the specified query to arrive, and then returns it.

Namespace: System.Management
Assembly: System.Management (in system.management.dll)

public ManagementBaseObject WaitForNextEvent ()
public ManagementBaseObject WaitForNextEvent ()
public function WaitForNextEvent () : ManagementBaseObject
Not applicable.

Return Value

A ManagementBaseObject representing the newly arrived event.

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.

.NET Framework Security

Full trust for the immediate caller. This member cannot be used by partially trusted code. For more information, see Using Libraries from Partially Trusted Code.

The following example shows how the client receives notification when an instance of Win32_Process is created because the event class is __InstanceCreationEvent. For more information, see the Windows Management Instrumentation documentation in the MSDN Library at http://msdn.microsoft.com/library. The client receives events synchronously by calling the WaitForNextEvent method. 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;
    }
}

Windows 98, Windows Server 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

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

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