Articolo
11/18/2011

AutomationEvent Class

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Represents an Automation event.

Inheritance Hierarchy

System.Object
System.Runtime.InteropServices.Automation.AutomationEvent

Namespace: System.Runtime.InteropServices.Automation
Assembly: System.Windows (in System.Windows.dll)

Syntax

'Declaration
Public NotInheritable Class AutomationEvent

public sealed class AutomationEvent

The AutomationEvent type exposes the following members.

Methods

	Name	Description
	AddEventHandler	Attaches the specified delegate to the Automation event.
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	RemoveEventHandler	Detaches the specified delegate from the Automation event.
	ToString	Returns a string that represents the current object. (Inherited from Object.)

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Events

	Name	Description
	EventRaised	Occurs when the Automation event occurs.

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Remarks

This class provides utility members for using managed event handlers to handle Automation events. It is the return value type of the AutomationFactory.GetEvent method.

In Visual Basic, you must use this class to handle Automation events. In C#, you can attach managed event handlers directly to Automation events by using the += syntax, and detach them using the -= syntax. However, in this case, the specified delegate must have a signature that exactly matches the Automation event signature.

Regardless of language, you can handle the EventRaised event without requiring knowledge of the Automation event signatures. The AddEventHandler and RemoveEventHandler methods provide alternatives that do require knowledge of the event signature.

For more information, see AutomationFactory and How to: Use Automation in Trusted Applications. For more information about Automation, see Automation.

Note:
Events with return values are not supported. Additionally, to use C# custom delegates with Automation events that have optional parameters, you must specify default parameter values in the delegate signature. In Visual Basic, delegate parameters cannot be optional, so you must handle the AutomationEvent.EventRaised event instead.

Examples

The following code example demonstrates how to handle Automation events.

This example is part of a larger example in How to: Use Automation in Trusted Applications.

Private Sub SearchEmail()

    UpdateStatusMessage("Searching Inbox for 'Silverlight'...")

    ' The following code demonstrates three ways to handle Automation 
    ' events. In Visual Basic, all three ways use the AutomationEvent class. 

    searchEvent =
        AutomationFactory.GetEvent(outlook, "AdvancedSearchComplete")

    ' The first way is demonstrated by the Handles clause of the 
    ' SearchEvent_EventRaised method, which requires the WithEvents modifier
    ' on the searchEvent variable declaration.

    ' The second way uses the AddHandler syntax with the EventRaised event,
    ' and does not require the WithEvents modifier. 
    ' AddHandler searchEvent.EventRaised, AddressOf SearchEvent_EventRaised

    ' The third way uses the AutomationEvent.AddEventHandler method, and
    ' requires the use of a delegate with an API signature that matches the
    ' Automation event. 
    ' searchEvent.AddEventHandler( 
    '   New AdvancedSearchCompleteDelegate(AddressOf SearchComplete))

    ' Begin the search.
    outlook.AdvancedSearch("Inbox",
        "urn:schemas:mailheader:subject ci_phrasematch 'Silverlight'",
        True, "SubjectSearch")

End Sub

Private WithEvents searchEvent As AutomationEvent

Sub SearchEvent_EventRaised(ByVal sender As Object,
    ByVal e As AutomationEventArgs) Handles searchEvent.EventRaised

    SearchComplete(e.Arguments(0))

End Sub

' Required only with the second two ways of handling Automation events. 
' Private Delegate Sub AdvancedSearchCompleteDelegate(ByRef search As Object)

' Note: Visual Basic does not support the use of custom delegates for 
' events with optional parameters. 

Private Sub SearchComplete(ByRef search As Object)

    Dim searchResults As New List(Of String)
    For Each result As Object In search.Results
        searchResults.Add(result.Subject)
    Next
    SetResultsList(searchResults)

End Sub

private void SearchEmail()
{
    UpdateStatusMessage("Searching Inbox for 'Silverlight'...");

    // The following code demonstrates three ways to handle Automation 
    // events. The first two ways use the AutomationEvent class. 
    // The last two ways require the use of a delegate with 
    // an API signature that matches the Automation event. 

    AutomationEvent searchEvent = AutomationFactory
        .GetEvent(outlook, "AdvancedSearchComplete");

    // The first way: 
    searchEvent.EventRaised += (sender, e) =>
    {
        SearchComplete(e.Arguments[0]);
    };

    // The second way:
    // searchEvent.AddEventHandler(
    //    new AdvancedSearchCompleteDelegate(SearchComplete));

    // The third way:
    // outlook.AdvancedSearchComplete +=
    //    new AdvancedSearchCompleteDelegate(SearchComplete);

    // Begin the search. 
    outlook.AdvancedSearch("Inbox",
        "urn:schemas:mailheader:subject ci_phrasematch 'Silverlight'",
        true, "SubjectSearch");
}

// Required only with the second two ways of handling Automation events. 
private delegate void AdvancedSearchCompleteDelegate(dynamic search);

// To use custom delegates for events with optional parameters, you
// must specify default values in the delegate signature as shown here:
// private delegate void MyEventHandlerDelegate(int i, float f=77);

private void SearchComplete(dynamic search)
{
    List<String> searchResults = new List<String>();
    foreach (dynamic result in search.Results) 
    { 
        searchResults.Add(result.Subject);
    }
    SetResultsList(searchResults);
}

Version Information

Silverlight

Supported in: 5, 4

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

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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