En la página:

this.AddProductRate.SubmitClicked += new SiteControls_AddRate.SubmitClickedHandler(
                        ShowRatesFromPage
                        );

En addproductrate:

    public delegate void SubmitClickedHandler();

    public event SubmitClickedHandler SubmitClicked;
    protected virtual void OnSubmitClicked()
    {
        // If an event has no subscribers registerd, it will
        // evaluate to null. The test checks that the value is not
        // null, ensuring that there are subsribers before
        // calling the event itself.
        if (SubmitClicked != null)
        {
            SubmitClicked();  // Notify Subscribers
        }
    }

Event handler in usercontrol

C#