EventQuery Class
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EventQuery Class


Represents a WMI event query.

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

public class EventQuery : ManagementQuery


Initializes a new instance of the EventQuery class. This is the default constructor.


Initializes a new instance of the EventQuery class for the specified query.

System_CAPS_pubmethodEventQuery(String, String)

Initializes a new instance of the EventQuery class for the specified language and query.


Gets or sets the query language used in the query string, defining the format of the query string. (Inherited from ManagementQuery.)


Gets or sets the query in text format. (Inherited from ManagementQuery.)


Returns a copy of the object. (Overrides ManagementQuery.Clone().)


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)


Serves as the default hash function. (Inherited from Object.)


Gets the Type of the current instance.(Inherited from Object.)


Creates a shallow copy of the current Object.(Inherited from Object.)


Parses 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.)


Returns a string that represents the current object.(Inherited from Object.)

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.

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
        EventQuery query = 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
        ManagementEventWatcher watcher =
            new ManagementEventWatcher(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
            "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

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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