Page and Control Event Sequence

**Teemu Keiski** · Jun 27 '08, 08:06 PM

Re: Page and Control Event Sequence

Hi,

I think it should work. Only downside with this approach is that you need
"tighter" coupling between the page and the control (e.g the control that's
listening for page's passthrough event needs to know more about the type of
the page, in practise some sort of interface etc)

Here's a sample

//INTERFACE - page implements

using System;

public interface IClickEventPage
{
event EventHandler Click;
}

//UC1 - raises an event

<%@ Control Language="C#" AutoEventWireup ="true"
CodeBehind="Web UserControl1.as cx.cs"
Inherits="WebAp plication2.WebU serControl1" %>
<asp:Button ID="Button1" runat="server"
Text="Clicking on this will raise UC's click event"
onclick="Button 1_Click" />

using System;
using System.Collecti ons.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.W ebControls;

namespace WebApplication2
{
public partial class WebUserControl1 : System.Web.UI.U serControl
{
private static readonly Object EventClick = new Object();

public event EventHandler Click
{
add
{
Events.AddHandl er(EventClick, value);
}
remove
{
Events.RemoveHa ndler(EventClic k, value);
}
}
protected void Page_Load(objec t sender, EventArgs e)
{

}

protected void Button1_Click(o bject sender, EventArgs e)
{
EventHandler h = Events[EventClick] as EventHandler;
if (h != null)
h(this, EventArgs.Empty );
}
}
}

//UC2 - listens for page's event
<%@ Control Language="C#" AutoEventWireup ="true"
CodeBehind="Web UserControl2.as cx.cs"
Inherits="WebAp plication2.WebU serControl2" %>
<asp:Label ID="lblInfo" runat="server" />

using System;
using System.Collecti ons.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.W ebControls;

namespace WebApplication2
{
public partial class WebUserControl2 : System.Web.UI.U serControl
{
protected override void OnInit(EventArg s e)
{
base.OnInit(e);
IClickEventPage p = Page as IClickEventPage ;
if(p != null)
{
p.Click += new EventHandler(p_ Click);
}

}

void p_Click(object sender, EventArgs e)
{
lblInfo.Text = "Something occurred, informed by the Page:" +
DateTime.Now.To String();
}
protected void Page_Load(objec t sender, EventArgs e)
{

}
}
}

//PAGE - acts as middle-man

<%@ Page Language="C#" AutoEventWireup ="true" CodeBehind="Def ault.aspx.cs"
Inherits="WebAp plication2._Def ault" %>

<%@ Register src="WebUserCon trol1.ascx" tagname="WebUse rControl1"
tagprefix="uc1" %>

<%@ Register src="WebUserCon trol2.ascx" tagname="WebUse rControl2"
tagprefix="uc2" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dt d">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>

<uc1:WebUserCon trol1 ID="USerControl 1" runat="server"
OnClick="UserCo ntrol1_Click" />

</div>
<uc2:WebUserCon trol2 ID="WebUserCont rol21" runat="server" />
</form>
</body>
</html>

using System;
using System.Collecti ons.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.W ebControls;

namespace WebApplication2
{

public partial class _Default : System.Web.UI.P age, IClickEventPage
{
protected void Page_Load(objec t sender, EventArgs e)
{

}

protected void UserControl1_Cl ick(object sender, EventArgs e)
{
EventHandler click = Events[EventClick] as EventHandler;
if (click != null)
click(this, e);

}

#region IClickEventPage Members

private static readonly Object EventClick = new Object();
public event EventHandler Click
{
add
{
Events.AddHandl er(EventClick, value);
}
remove
{
Events.RemoveHa ndler(EventClic k, value);
}
}

#endregion
}
}

--
Teemu Keiski
AspInsider, ASP.NET MVP

http://blogs.aspadvice.com/joteke

http://teemukeiski.net

"Jordan S." <A@B.comwrote in message
news:O56rke3tIH A.1220@TK2MSFTN GP04.phx.gbl...

I'm just wondering if this would work. Please note that I'm not asking
*how* to raise events. I'm clear on that. What I'm not clear on is the
sequence in which events are raised by custom controls relative to the
hosting Page, and therefore if the following specific arrangement would
even work.
>
What I'm looking to do is dynamically insert multiple custom composite Web
server controls onto a blank Page. This is no problem, I know how to do
this part.
>
What I need is for one of these controls to "broadcast" events of interest
to any other controls on the hosting Page that may be interested. But I do
not want for any of the controls on the page to directly know anything
about each other (hold references to each other).
>
So, to make this happen I am thinking that this would work:
A control gets notified - via the hosting Page - of the event originating
in another control.
>
Specifically:
>
1. During PostBack, control #1 raises an event (that is of interest to
Control #2).
>
2. The hosting Page is subscribed to the event in Control #1
>
3. The hosting page then raises an event of its own, passing along the
EventArgs received from Control #1.
>
4. Control #2 is subscribed to the Page's event [that is raised in step 3
above], and consequently receives notification (from the Page) that
includes a copy of the EventArgs-derived class sent from Control #1.
>
Will this work? Will ASP.NET, during PostBack, raise the events in the
correct sequence? (Control riases event ----- page raises another
ent ----- Control handles event raised by Page)
>
Thanks!
>
>
>
>

Page and Control Event Sequence

Page and Control Event Sequence

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