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ManagementEventWatcher Constructor (EventQuery)

Initializes a new instance of the ManagementEventWatcher class when given a WMI event query.

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

'Declaration
Public Sub New ( _
	query As EventQuery _
)

Parameters

query
Type: System.Management.EventQuery

An EventQuery representing a WMI event query, which determines the events for which the watcher will listen.

The namespace in which the watcher will be listening for events is the default namespace that is currently set.

.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.

In this code example, 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.

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 String
        query = "SELECT * FROM __InstanceCreationEvent " _
            & "WITHIN 1 WHERE " & _
            "TargetInstance isa ""Win32_Process""" 

        ' Initialize an event watcher and subscribe to events  
        ' that match this query 
        Dim watcher As New ManagementEventWatcher(New EventQuery( _
        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

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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