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EventQuery Class
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EventQuery Class

Represents a WMI event query.

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

'Declaration
Public Class EventQuery _
	Inherits ManagementQuery

The EventQuery type exposes the following members.

  NameDescription
Public methodEventQueryInitializes a new instance of the EventQuery class. This is the default constructor.
Public methodEventQuery(String)Initializes a new instance of the EventQuery class for the specified query.
Public methodEventQuery(String, String)Initializes a new instance of the EventQuery class for the specified language and query.
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  NameDescription
Public propertyQueryLanguageGets or sets the query language used in the query string, defining the format of the query string. (Inherited from ManagementQuery.)
Public propertyQueryStringGets or sets the query in text format. (Inherited from ManagementQuery.)
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  NameDescription
Public methodCloneReturns a copy of the object. (Overrides ManagementQuery.Clone.)
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Protected methodParseQueryParses the query string and sets the property values accordingly. If the query is valid, the class name property and condition property of the query will be parsed. (Inherited from ManagementQuery.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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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.

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 New EventQuery
        query.QueryString = "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(query)
        ' times watcher.WaitForNextEvent in 5 seconds
        watcher.Options.Timeout = New TimeSpan(0, 0, 50)

        ' 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

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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