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ManagementEventWatcher Constructors

  • Reference

Definition

Namespace:
System.Management
Assembly:
System.Management.dll
Package:
System.Management v8.0.0
Package:
System.Management v9.0.0-rc.2.24473.5

Initializes a new instance of the ManagementEventWatcher class.

Overloads

ManagementEventWatcher()

Initializes a new instance of the ManagementEventWatcher class. For further initialization, set the properties on the object. This is the parameterless constructor.
ManagementEventWatcher(EventQuery)

Initializes a new instance of the ManagementEventWatcher class when given a WMI event query.
ManagementEventWatcher(String)

Initializes a new instance of the ManagementEventWatcher class when given a WMI event query in the form of a string.
ManagementEventWatcher(ManagementScope, EventQuery)

Initializes a new instance of the ManagementEventWatcher class that listens for events conforming to the given WMI event query.
ManagementEventWatcher(String, String)

Initializes a new instance of the ManagementEventWatcher class that listens for events conforming to the given WMI event query. For this variant, the query and the scope are specified as strings.
ManagementEventWatcher(ManagementScope, EventQuery, EventWatcherOptions)

Initializes a new instance of the ManagementEventWatcher class that listens for events conforming to the given WMI event query, according to the specified options. For this variant, the query and the scope are specified objects. The options object can specify options such as time-out and context information.
ManagementEventWatcher(String, String, EventWatcherOptions)

Initializes a new instance of the ManagementEventWatcher class that listens for events conforming to the given WMI event query, according to the specified options. For this variant, the query and the scope are specified as strings. The options object can specify options such as a time-out and context information.

ManagementEventWatcher()

Source:
ManagementEventWatcher.cs
Source:
ManagementEventWatcher.cs

Initializes a new instance of the ManagementEventWatcher class. For further initialization, set the properties on the object. This is the parameterless constructor.

public:
 ManagementEventWatcher();
public ManagementEventWatcher ();
Public Sub New ()

Examples

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. 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
        WqlEventQuery query =
            new WqlEventQuery("__InstanceCreationEvent",
            new TimeSpan(0,0,1),
            "TargetInstance isa \"Win32_Process\"");

        // Initialize an event watcher and subscribe to events
        // that match this query
        ManagementEventWatcher watcher =
            new ManagementEventWatcher();
        watcher.Query = 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;
    }
}

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 WqlEventQuery( _
            "__InstanceCreationEvent", _
            New TimeSpan(0, 0, 1), _
            "TargetInstance isa ""Win32_Process""")

        ' Initialize an event watcher and subscribe to events 
        ' that match this query
        Dim watcher As New ManagementEventWatcher
        watcher.Query = query
        ' times 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.")
        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

Remarks

.NET Framework Security

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.

Applies to

ManagementEventWatcher(EventQuery)

Source:
ManagementEventWatcher.cs
Source:
ManagementEventWatcher.cs

Initializes a new instance of the ManagementEventWatcher class when given a WMI event query.

public:
 ManagementEventWatcher(System::Management::EventQuery ^ query);
public ManagementEventWatcher (System.Management.EventQuery query);
new System.Management.ManagementEventWatcher : System.Management.EventQuery -> System.Management.ManagementEventWatcher
Public Sub New (query As EventQuery)

Parameters

query
EventQuery

An EventQuery representing a WMI event query, which determines the events for which the watcher will listen.

Examples

In this code example, 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. 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\"";

        // Initialize an event watcher and subscribe to events
        // that match this query
        ManagementEventWatcher watcher =
            new ManagementEventWatcher(new EventQuery(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;
    }
}

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 String
        query = "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(New EventQuery( _
        query))

        ' times 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.")
        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

Remarks

The namespace in which the watcher will be listening for events is the default namespace that is currently set.

.NET Framework Security

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.

Applies to

ManagementEventWatcher(String)

Source:
ManagementEventWatcher.cs
Source:
ManagementEventWatcher.cs

Initializes a new instance of the ManagementEventWatcher class when given a WMI event query in the form of a string.

public:
 ManagementEventWatcher(System::String ^ query);
public ManagementEventWatcher (string query);
new System.Management.ManagementEventWatcher : string -> System.Management.ManagementEventWatcher
Public Sub New (query As String)

Parameters

query
String

A WMI event query, which defines the events for which the watcher will listen.

Examples

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. 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\"";

        // 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;
    }
}

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 String
        query = "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, 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.")
        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

Remarks

The namespace in which the watcher will be listening for events is the default namespace that is currently set.

.NET Framework Security

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.

Applies to

ManagementEventWatcher(ManagementScope, EventQuery)

Source:
ManagementEventWatcher.cs
Source:
ManagementEventWatcher.cs

Initializes a new instance of the ManagementEventWatcher class that listens for events conforming to the given WMI event query.

public:
 ManagementEventWatcher(System::Management::ManagementScope ^ scope, System::Management::EventQuery ^ query);
public ManagementEventWatcher (System.Management.ManagementScope scope, System.Management.EventQuery query);
new System.Management.ManagementEventWatcher : System.Management.ManagementScope * System.Management.EventQuery -> System.Management.ManagementEventWatcher
Public Sub New (scope As ManagementScope, query As EventQuery)

Parameters

scope
ManagementScope

A ManagementScope representing the scope (namespace) in which the watcher will listen for events.

query
EventQuery

An EventQuery representing a WMI event query, which determines the events for which the watcher will listen.

Examples

In this code example, 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. 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\"";

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

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 String
        query = "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( _
            New ManagementScope("root\CIMV2"), _
            New EventQuery(query))

        ' times 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.")
        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

Remarks

.NET Framework Security

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.

Applies to

ManagementEventWatcher(String, String)

Source:
ManagementEventWatcher.cs
Source:
ManagementEventWatcher.cs

Initializes a new instance of the ManagementEventWatcher class that listens for events conforming to the given WMI event query. For this variant, the query and the scope are specified as strings.

public:
 ManagementEventWatcher(System::String ^ scope, System::String ^ query);
public ManagementEventWatcher (string scope, string query);
new System.Management.ManagementEventWatcher : string * string -> System.Management.ManagementEventWatcher
Public Sub New (scope As String, query As String)

Parameters

scope
String

The management scope (namespace) in which the watcher will listen for events.

query
String

The query that defines the events for which the watcher will listen.

Examples

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. 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\"";

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

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 String
        query = "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( _
            "root\CIMV2", query)

        ' times 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.")
        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

Remarks

.NET Framework Security

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.

Applies to

ManagementEventWatcher(ManagementScope, EventQuery, EventWatcherOptions)

Source:
ManagementEventWatcher.cs
Source:
ManagementEventWatcher.cs

Initializes a new instance of the ManagementEventWatcher class that listens for events conforming to the given WMI event query, according to the specified options. For this variant, the query and the scope are specified objects. The options object can specify options such as time-out and context information.

public:
 ManagementEventWatcher(System::Management::ManagementScope ^ scope, System::Management::EventQuery ^ query, System::Management::EventWatcherOptions ^ options);
public ManagementEventWatcher (System.Management.ManagementScope scope, System.Management.EventQuery query, System.Management.EventWatcherOptions options);
new System.Management.ManagementEventWatcher : System.Management.ManagementScope * System.Management.EventQuery * System.Management.EventWatcherOptions -> System.Management.ManagementEventWatcher
Public Sub New (scope As ManagementScope, query As EventQuery, options As EventWatcherOptions)

Parameters

scope
ManagementScope

A ManagementScope representing the scope (namespace) in which the watcher will listen for events.

query
EventQuery

An EventQuery representing a WMI event query, which determines the events for which the watcher will listen.

options
EventWatcherOptions

An EventWatcherOptions representing additional options used to watch for events.

Examples

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. 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, so wait for 1 event to return
        EventWatcherOptions options = new EventWatcherOptions(
            null, TimeSpan.MaxValue, 1);

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

        // 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;
    }
}

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 String
        query = "SELECT * FROM __InstanceCreationEvent " _
            & "WITHIN 1 WHERE " & _
            "TargetInstance isa ""Win32_Process"""

        ' Event options
        ' blockSize = 1, so wait for 1 event to return
        Dim options As New EventWatcherOptions( _
            Nothing, TimeSpan.MaxValue, 1)


        ' Initialize an event watcher and subscribe to events 
        ' that match this query
        Dim watcher As New ManagementEventWatcher( _
            New ManagementScope("root\CIMV2"), _
            New EventQuery(query), _
            options)

        ' 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

Remarks

.NET Framework Security

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.

Applies to

ManagementEventWatcher(String, String, EventWatcherOptions)

Source:
ManagementEventWatcher.cs
Source:
ManagementEventWatcher.cs

Initializes a new instance of the ManagementEventWatcher class that listens for events conforming to the given WMI event query, according to the specified options. For this variant, the query and the scope are specified as strings. The options object can specify options such as a time-out and context information.

public:
 ManagementEventWatcher(System::String ^ scope, System::String ^ query, System::Management::EventWatcherOptions ^ options);
public ManagementEventWatcher (string scope, string query, System.Management.EventWatcherOptions options);
new System.Management.ManagementEventWatcher : string * string * System.Management.EventWatcherOptions -> System.Management.ManagementEventWatcher
Public Sub New (scope As String, query As String, options As EventWatcherOptions)

Parameters

scope
String

The management scope (namespace) in which the watcher will listen for events.

query
String

The query that defines the events for which the watcher will listen.

options
EventWatcherOptions

An EventWatcherOptions representing additional options used to watch for events.

Examples

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. 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, so wait for 1 event to return
        EventWatcherOptions options = new EventWatcherOptions(
            null, TimeSpan.MaxValue, 1);

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

        // 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;
    }
}

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 String
        query = "SELECT * FROM __InstanceCreationEvent " _
            & "WITHIN 1 WHERE " & _
            "TargetInstance isa ""Win32_Process"""

        ' Event options
        ' blockSize = 1, so wait for 1 event to return
        Dim options As New EventWatcherOptions( _
            Nothing, TimeSpan.MaxValue, 1)


        ' Initialize an event watcher and subscribe to events 
        ' that match this query
        Dim watcher As New ManagementEventWatcher( _
            "root\CIMV2", _
            query, _
            options)

        ' 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

Remarks

.NET Framework Security

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.

Applies to