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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

The EventQuery type exposes the following members.

  NameDescription
Public methodEventQuery()Initializes 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.

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
        Console.WriteLine(
            "Open an application (notepad.exe) to trigger an event.");
        ManagementBaseObject e = watcher.WaitForNextEvent();

        //Display information from the event
        Console.WriteLine(
            "Process {0} has been created, path is: {1}", 
            ((ManagementBaseObject)e
            ["TargetInstance"])["Name"],
            ((ManagementBaseObject)e
            ["TargetInstance"])["ExecutablePath"]);

        //Cancel the subscription
        watcher.Stop();
        return 0;
    }
}

.NET Framework

Supported in: 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows Phone 8.1, Windows Phone 8, 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.

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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