Question

How does one actually expose a abstracted event from asp.net usercontrol[ascx file] to the container webforms page. This is my scenario,

1. I created a webforms usercontrol a ascx file and put a databound checkboxlist with a validator to validate it(I know this could be done webforms itself why a usercontrol u ask, but it’s a scenario)

2. Now i wanted to expose a event to the container page called OnValidating which would produce the result of validation

signature of the event is below:

public delegate void Validating(object source,EventArgs e);

public event Validating OnValidating;

public void InvokeOnValidating(EventArgs e)
        {
            Validating handler = OnValidating;
            if (handler != null) handler(this, e);
        }

As per the msdn documentation, the page framework handles the event subscribing and unsubscribing. So all i need to do was invoke the event when validation fails. Great i was happy but,

1. I couldn’t show up the event in the properties window when all other public propertes did

2. Why the hell is my event invoker[InvokeOnValidating], event delegate[Validating] shown in intellisense list when i type usercontrolid. along with the event[OnValidating]. I want only the event to be exposed.

3. Also can i allow page to subscribe to event TextboxChanged created inside the usercontrol? If so get me the code.

Note: I would love to see more code than lengthy explanations

Answer 1

You’re mixing concepts, you don’t need a delegate to register events, try this code, and i’ll explain the changes and attempt to answer your questions below

    public event EventHandler Validating;
    private void OnValidating(EventArgs ea)
    {
        var e = Validating;
        if (e != null)
            e(this, ea);
    }

On the page with the control use, notice the On, the framework adds this for all events:

<uc:MyUserControl OnValidating="myhandlermethodinpage" />

1. VS is not 100% accurate with this, sometimes properties of controls don’t show up! Intelissence is more reliable
2. Because they weren’t set as private, only the event should be public.
3. Not sure that will be possible, you’ll need to capture the event of the textbox in the control and make it raise it’s own new event.

Couldn’t add on comment, but basically if you need custom event args do as such:

    public event EventHandler<CustomEventArgs> Validating;
private void OnValidating(CustomEventArgs ea)
{
    var e = Validating;
    if (e != null)
        e(this, ea);
}
public class CustomEventArgs:EventArgs{
    public int MyProperty { get; set; }
}