Pass Link-Button Click from One User Control to Another - asp.net

Question

I have two user controls on the same page. One contains a ListView that displays navigation links, the second user control should be updated when user clicks on the buttonlink in the ListView. How can I do this?

Answer 1

UserControl A should handle the button-click and raise a custom event declared in the UserControl
The page handles this event and calls a public method of UserControl B that updates it's content
You could pass necessary informations from UserControl A to page via EventArgs(or pass the UserControl itself as argument and use it's public properties).
The page then passes the arguments to UserControl B via method parameter or by changing it's public properties before calling the Update-Method.
http://msdn.microsoft.com/en-us/library/fb3w5b53.aspx
http://chiragrdarji.blogspot.com/2007/08/raise-event-from-user-control-to-main.html
Here is the sample code you've requested.
Sorry for the meaningless naming but you haven't told what's this all about. You should use readable variables,properties,method and event-names instead.
Reduced UserControl A with a ListView:
<%# Control Language="vb" AutoEventWireup="false" CodeBehind="UsercontrolA.ascx.vb" Inherits="WebApplication1.UserControlA" %>
<asp:ListView ID="ListView1" runat="server">
<ItemTemplate>
<asp:LinkButton ID="LinkButton1"
CommandName="LinkClick"
CommandArgument='<%#Eval("ID") %>'
runat="server"
Text='<%#Eval("Text") %>'></asp:LinkButton>
</ItemTemplate>
</asp:ListView>
Removed the ListView databinding from codebehind because that doesn't matter. The important part is handling the ListView's ItemCommand and raising the custom event:
Public Event LinkClicked(sender As UserControlA, id As Int32)
Private Sub LV_ItemCommand(sender As Object, e As ListViewCommandEventArgs) Handles ListView1.ItemCommand
If e.CommandName = "LinkClick" Then
Dim id = CType(e.CommandArgument, Int32)
' This is the best way for UC's to commmunicate with the page: '
RaiseEvent LinkClicked(Me, id)
End If
End Sub
Simple UserControl B with nothing more than a Label(ascx):
<%# Control Language="vb" AutoEventWireup="false" CodeBehind="UserControlB.ascx.vb" Inherits="WebApplication1.UserControlB" %>
<asp:Label ID="Label1" runat="server"></asp:Label>
With an Update-Method in codebehind:
Public Sub Update(showID As Int32)
Me.Label1.Text = String.Format("Link {0} clicked", showID.ToString)
End Sub
Finally, here is the Page(aspx)
<uc1:UsercontrolA ID="UC_A" runat="server" />
<br />
<uc2:UserControlB ID="UC_B" runat="server" />
It controls both UserControls. It handles the event from UserControl A and calls the Update-Method that UserControl B provides:
Private Sub LinkClicked(sender As UserControlA, id As Integer) Handles UC_A.LinkClicked
Me.UC_B.Update(id)
End Sub
The advantage of this event-approach is that UserControls stay being reusable. You can use UserControl A in other pages as well even when they don't handle this event. It's part of the controller to decide what is needed and what should be done.
UserControls as a rule should not depend on specific controllers, otherwise they are hard-linked and not reusable. That would be also a good source for nasty erros. A UserControl might be a controller for other nested (User-)Controls but not for the page itself.
Communication Summary:
Page -> UserControl -> public properties and methods
UserControl -> Page -> Events
UserControl -> UserControl -> the controller-UserControl adopts the page-role(see above)