Get-Event Subscriber

Syntax

Get-EventSubscriber
   [[-SourceIdentifier] <String>]
   [-Force]
   [<CommonParameters>]

Get-EventSubscriber
   [-SubscriptionId] <Int32>
   [-Force]
   [<CommonParameters>]

Description

The Get-EventSubscriber cmdlet gets the event subscribers in the current session.

When you subscribe to an event by using a Register event cmdlet, an event subscriber is added to your Windows PowerShell session, and the events to which you subscribed are added to your event queue whenever they are raised. To cancel an event subscription, delete the event subscriber by using the Unregister-Event cmdlet.

Examples

Example 1: Get the event subscriber for a timer event

PS C:\> $Timer = New-Object Timers.Timer

PS C:\> $Timer | Get-Member -Type Event

PS C:\> Register-ObjectEvent -InputObject $Timer -EventName Elapsed -SourceIdentifier Timer.Elapsed

PS C:\> Get-EventSubscriber

PS C:\> $Timer = New-Object Timers.Timer

PS C:\> $Timer | Get-Member -Type Event

TypeName: System.Timers.Timer

Name     MemberType Definition

----     ---------- ----------

Disposed Event      System.EventHandler Disposed(System.Object, System.EventArgs)

Elapsed  Event      System.Timers.ElapsedEventHandler Elapsed(System.Object, System.Timers.ElapsedEventArgs) PS C:\> Register-ObjectEvent -InputObject $Timer -EventName Elapsed -SourceIdentifier Timer.Elapsed

PS C:\> Get-EventSubscriber

SubscriptionId   : 4

SourceObject     : System.Timers.Timer

EventName        : Elapsed

SourceIdentifier : Timer.Elapsed

Action           :

HandlerDelegate  :

SupportEvent     : False

ForwardEvent     : False

This example uses a Get-EventSubscriber command to get the event subscriber for a timer event.

The first command uses the New-Object cmdlet to create an instance of a timer object. It saves the new timer object in the $Timer variable.

The second command uses the Get-Member cmdlet to display the events that are available for timer objects. The command uses the Type parameter of the Get-Member cmdlet with a value of Event.

The third command uses the Register-ObjectEvent cmdlet to register for the Elapsed event on the timer object.

The fourth command uses the Get-EventSubscriber cmdlet to get the event subscriber for the Elapsed event.

Example 2: Use the dynamic module in PSEventJob in the Action property of the event subscriber

PS C:\> $Timer = New-Object Timers.Timer

PS C:\> $Timer.Interval = 500

PS C:\> Register-ObjectEvent -InputObject $Timer -EventName Elapsed -SourceIdentifier Timer.Random -Action { $Random = Get-Random -Min 0 -Max 100 }

Id  Name           State      HasMoreData  Location  Command

--  ----           -----      -----------  --------  -------

3   Timer.Random   NotStarted False                  $Random = Get-Random ... PS C:\> $Timer.Enabled = $True

PS C:\> $Subscriber = Get-EventSubcriber -SourceIdentifer Timer.Random

PS C:\> ($Subscriber.action).gettype().fullname

PSEventJob PS C:\> $Subscriber.action | Format-List -Property *

State         : Running

Module        : __DynamicModule_6b5cbe82-d634-41d1-ae5e-ad7fe8d57fe0

StatusMessage :

HasMoreData   : True

Location      :

Command       : $random = Get-Random -Min 0 -Max 100

JobStateInfo  : Running

Finished      : System.Threading.ManualResetEvent

InstanceId    : 88944290-133d-4b44-8752-f901bd8012e2

Id            : 1

Name          : Timer.Random

ChildJobs     : {}

... PS C:\> & $Subscriber.action.module {$Random}

96 PS C:\> & $Subscriber.action.module {$Random}

23

This example shows how to use the dynamic module in the PSEventJob object in the Action property of the event subscriber.

The first command uses the New-Object cmdlet to create a timer object. The second command sets the interval of the timer to 500 (milliseconds).

The third command uses the Register-ObjectEvent cmdlet to register the Elapsed event of the timer object. The command includes an action that handles the event. Whenever the timer interval elapses, an event is raised and the commands in the action run. In this case, the Get-Random cmdlet generates a random number between 0 and 100 and saves it in the $Random variable. The source identifier of the event is Timer.Random.

When you use an Action parameter in a Register-ObjectEvent command, the command returns a PSEventJob object that represents the action.

The fourth command enables the timer.

The fifth command uses the Get-EventSubscriber cmdlet to get the event subscriber of the Timer.Random event. It saves the event subscriber object in the $Subscriber variable.

The sixth command shows that the Action property of the event subscriber object contains a PSEventJob object. In fact, it contains the same PSEventJob object that the Register-ObjectEvent command returned.

The seventh command uses the Format-List cmdlet to display all of the properties of the PSEventJob object in the Action property in a list. The result reveals that the PSEventJob object has a Module property that contains a dynamic script module that implements the action.

The remaining commands use the call operator (&) to invoke the command in the module and display the value of the $Random variable. You can use the call operator to invoke any command in a module, including commands that are not exported. In this case, the commands show the random number that is being generated when the Elapsed event occurs.

For more information about modules, see about_Modules.

Required Parameters

Optional Parameters

Inputs

None

You cannot pipe input to this cmdlet.

Outputs

System.Management.Automation.PSEventSubscriber

Get-EventSubscriber returns an object that represents each event subscriber.

Notes

• The New-Event cmdlet, which creates a custom event, does not generate a subscriber. Therefore, the Get-EventSubscriber cmdlet will not find a subscriber object for these events. However, if you use the Register-EngineEvent cmdlet to subscribe to a custom event (in order to forward the event or to specify an action), Get-EventSubscriber will find the subscriber that Register-EngineEvent generates.

  Events, event subscriptions, and the event queue exist only in the current session. If you close the current session, the event queue is discarded and the event subscription is canceled.

*

Related Links

• Get-Event
• New-Event
• Register-EngineEvent
• Register-ObjectEvent
• Remove-Event
• Unregister-Event
• Wait-Event