WqlEventQuery Class
Represents a WMI event query in WQL format.
For a list of all members of this type, see WqlEventQuery Members.
System.Object
System.Management.ManagementQuery
System.Management.EventQuery
System.Management.WqlEventQuery
[Visual Basic] Public Class WqlEventQuery Inherits EventQuery [C#] public class WqlEventQuery : EventQuery [C++] public __gc class WqlEventQuery : public EventQuery [JScript] public class WqlEventQuery extends EventQuery
Thread Safety
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
Example
[C#] using System; using System.Management; // This sample demonstrates how to subscribe to an event // using a WQL event query. class Sample_EventQuery { public static int Main(string[] args) { //For this example, we make sure we have an arbitrary class on root\default ManagementClass newClass = new ManagementClass( "root\\default", String.Empty, null); newClass["__Class"] = "TestWql"; newClass.Put(); //Create a query object for watching for class deletion events WqlEventQuery eventQuery = new WqlEventQuery("select * from __classdeletionevent"); //Initialize an event watcher object with this query ManagementEventWatcher watcher = new ManagementEventWatcher( new ManagementScope("root/default"), eventQuery); //Set up a handler for incoming events MyHandler handler = new MyHandler(); watcher.EventArrived += new EventArrivedEventHandler(handler.Arrived); //Start watching for events watcher.Start(); //For this example, we delete the class to trigger an event newClass.Delete(); //Nothing better to do - we loop to wait for an event to arrive. while (!handler.IsArrived) { System.Threading.Thread.Sleep(1000); } //In this example we only want to wait for one event, so we can stop watching watcher.Stop(); return 0; } public class MyHandler { private bool isArrived = false; //Handles the event when it arrives public void Arrived(object sender, EventArrivedEventArgs e) { ManagementBaseObject eventArg = (ManagementBaseObject)(e.NewEvent["TargetClass"]); Console.WriteLine("Class Deleted = " + eventArg["__CLASS"]); isArrived = true; } //Used to determine whether the event has arrived or not. public bool IsArrived { get { return isArrived; } } } } [Visual Basic] Imports System Imports System.Management ' This sample demonstrates how to subscribe an event ' using a WQL event query. Class Sample_EventQuery Public Shared Sub Main() 'For this example, we make sure we have an arbitrary class on root\default Dim newClass As New ManagementClass( _ "root\default", _ String.Empty, Nothing) newClass("__Class") = "TestWql" newClass.Put() 'Create a query object for watching for class deletion events Dim eventQuery As New WqlEventQuery("select * from __classdeletionevent") 'Initialize an event watcher object with this query Dim watcher As New ManagementEventWatcher( _ New ManagementScope("root/default"), _ eventQuery) 'Set up a handler for incoming events Dim handler As New MyHandler() AddHandler watcher.EventArrived, AddressOf handler.Arrived 'Start watching for events watcher.Start() 'For this example, we delete the class to trigger an event newClass.Delete() 'Nothing better to do - we loop to wait for an event to arrive. While Not handler.IsArrived Console.Write("0") System.Threading.Thread.Sleep(1000) End While 'In this example we only want to wait for one event, so we can stop watching watcher.Stop() End Sub Public Class MyHandler Private _isArrived As Boolean = False 'Handles the event when it arrives Public Sub Arrived(sender As Object, e As EventArrivedEventArgs) Dim eventArg As ManagementBaseObject = CType( _ e.NewEvent("TargetClass"), _ ManagementBaseObject) Console.WriteLine(("Class Deleted = " + eventArg("__CLASS"))) _isArrived = True End Sub 'Used to determine whether the event has arrived or not. Public ReadOnly Property IsArrived() As Boolean Get Return _isArrived End Get End Property End Class End Class
[C++, JScript] No example is available for C++ or JScript. To view a Visual Basic or C# example, click the Language Filter button
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Requirements
Namespace: System.Management
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family
Assembly: System.Management (in System.Management.dll)