AutomationEvent.AddEventHandler Method


Attaches the specified delegate to the Automation event.

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

public void AddEventHandler(
	Delegate handler


Type: System.Delegate
The delegate to attach to the event.

This method requires the attached delegate to have a signature that exactly matches the Automation event signature. Alternately, you can use the EventRaised event, which does not require knowledge of the Automation event signature.

For more information, see AutomationFactory. For more information about Automation, see Automation.


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.

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 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) =>

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

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

    // Begin the search. 
        "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) 


Supported in: 5, 4

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1

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

Community Additions