ManagementEventWatcher Constructor (String, String, EventWatcherOptions)

ManagementEventWatcher Constructor (String, String, EventWatcherOptions)


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.

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

public ManagementEventWatcher(
	string scope,
	string query,
	EventWatcherOptions options


Type: System.String

The management scope (namespace) in which the watcher will listen for events.

Type: System.String

The query that defines the events for which the watcher will listen.

Type: System.Management.EventWatcherOptions

An EventWatcherOptions representing additional options used to watch for events.

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 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
        string query = 
            "SELECT * FROM __InstanceCreationEvent "
            + "WITHIN 1 WHERE " +
            "TargetInstance isa \"Win32_Process\"";

        // Event options
        // blockSize = 1, so wait for 1 event to return
        EventWatcherOptions options = new EventWatcherOptions(
            null, TimeSpan.MaxValue, 1);

        // Initialize an event watcher and subscribe to events 
        // that match this query
        ManagementEventWatcher watcher =
            new ManagementEventWatcher(
            new ManagementScope("root\\CIMV2"),
            new EventQuery(query), options);

        // Block until the next event occurs 
        // Note: this can be done in a loop if waiting for 
        //        more than one occurrence
            "Open an application (notepad.exe) to trigger an event.");
        ManagementBaseObject e = watcher.WaitForNextEvent();

        //Display information from the event
            "Process {0} has been created, path is: {1}", 

        //Cancel the subscription
        return 0;

.NET Framework
Available since 1.1
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