EventWatcherOptions Constructor (ManagementNamedValueCollection, TimeSpan, Int32)

 

Initializes a new instance of the EventWatcherOptions class with the given values.

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

public EventWatcherOptions(
	ManagementNamedValueCollection context,
	TimeSpan timeout,
	int blockSize
)

Parameters

context
Type: System.Management.ManagementNamedValueCollection

The options context object containing provider-specific information to be passed through to the provider.

timeout
Type: System.TimeSpan

The time-out to wait for the next events.

blockSize
Type: System.Int32

The number of events to wait for in each block.

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.

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
        string query = "SELECT * FROM" +
            " __InstanceCreationEvent WITHIN 1 " + 
            "WHERE TargetInstance isa \"Win32_Process\"";

        // Event options
        // blockSize = 1 to receive one event
        EventWatcherOptions eventOptions = new
            EventWatcherOptions(null, System.TimeSpan.MaxValue,
            1);

        // Initialize an event watcher and subscribe to events 
        // that match this query
        ManagementEventWatcher watcher =
            new ManagementEventWatcher("root\\CIMV2", query,
            eventOptions);

        // 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
Available since 1.1
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