ManagementEventWatcher Class (System.Management)

Examples

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. 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;
   
    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
    
     Initializes a new instance of the
     
      ManagementEventWatcher
     
     class that listens for events conforming to the given WMI event query, according to the specified options. For this variant, the query and the scope are specified objects. The options object can specify options such as time-out and context information.
    
    
     Initializes a new instance of the
     
      ManagementEventWatcher
     
     class that listens for events conforming to the given WMI
     
      event query
     
     , according to the specified options. For this variant, the query and the scope are specified as strings. The options object can specify options such as a time-out and context information.
    
    
     Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object.
    
    (Inherited from
    
     MarshalByRefObject
    
    )
    
     Releases the unmanaged resources used by the
     
      Component
     
     and optionally releases the managed resources.
    
    (Inherited from
    
     Component
    
    )
    
     Obsolete.
    
    
     Retrieves the current lifetime service object that controls the lifetime policy for this instance.
    
    (Inherited from
    
     MarshalByRefObject
    
    )
    
     Returns an object that represents a service provided by the
     
      Component
     
     or by its
     
      Container
     
     .
    
    (Inherited from
    
     Component
    
    )
    
     Obsolete.
    
    
     Obtains a lifetime service object to control the lifetime policy for this instance.
    
    (Inherited from
    
     MarshalByRefObject
    
    )
    
     Returns a
     
      String
     
     containing the name of the
     
      Component
     
     , if any. This method should not be overridden.
    
    (Inherited from
    
     Component
    
    )