Eventhandling in ascx usercontrols

Question

What is best practises for communicating events from a usercontrol to parent control/page i want to do something similar to this:

MyPage.aspx:


        

Answer 1

I found the same solution on OdeToCode that @lordscarlet linked to in his accepted solution. The problem was that I needed a solution in VB rather than C#. It didn't translate perfectly. Specifically, checking if the event handler is null in OnBubbleClick didn't work in VB because the compiler thought I was trying to call the event, and was giving an error that said "... cannot be called directly. Use a 'RaiseEvent' statement to raise an event." So here's a VB translation for the OdeToCode solution, using a control called CountryDropDownList.

For starters, let’s create a user control with a dropdown attached.

<%@ Control Language="vb" AutoEventWireup="false" CodeBehind="CountryDropDownList.ascx.vb" Inherits="CountryDropDownList" %>

    
    United States
    Afghanistan
    Albania

The code behind for the user control looks like the following.

Public Class CountryDropDownList
    Inherits System.Web.UI.UserControl
    Public Event SelectedCountryChanged As EventHandler

    Protected Sub ddlCountryList_SelectedIndexChanged(sender As Object, e As EventArgs)
        ' bubble the event up to the parent
        RaiseEvent SelectedCountryChanged(Me, e)
    End Sub
End Class

An ASPX page can now put the user control to work.

<%@ Page Language="vb" AutoEventWireup="false" CodeBehind="UpdateProfile.aspx.vb" Inherits="UpdateProfile" MaintainScrollPositionOnPostback="true" %>
<%@ Register Src="~/UserControls/CountryDropDownList.ascx" TagPrefix="SO" TagName="ucCountryDropDownList" %>


    
        
    
    
        

            
        
    

In the code behind for the page:

Protected Sub OnSelectedCountryChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ddlCountry.SelectedCountryChanged
    ' add your code here
End Sub