DropDownList - SelectedIndexCh anged doesn't fire

[Damien]

Hi guys,

I'm trying to learn ASP.NET and got a problem with DroDownList...
SelectedIndexCh anged doesn't fire.
Maybe you'll be able to suggest something.

I think it may be connected with the fact I fill this list dynamically.

I use the following code:

--presentation--
<%@ Page Language="C#" MasterPageFile= "~/Site.master"
AutoEventWireup ="true" CodeFile="index .aspx.cs"
Inherits="Pagin gAndSorting_ind ex" Title="Untitled Page" %>
<asp:Content ID="Content1" ContentPlaceHol derID="MainCont ent"
Runat="Server">
<br />
<asp:Label ID="PageInfo" runat="server"
Text="Label"></asp:Label>&nbsp ;<asp:DropDownL ist ID="PageList"
runat="server" AutoPostBack="T rue"
OnSelectedIndex Changed="PageLi st_SelectedInde xChanged">
</asp:DropDownLis t><br />
<br />
<asp:GridView ID="Products" runat="server"
AutoGenerateCol umns="False" DataKeyNames="P roductID"
DataSourceID="O bjectDataSource 1" AllowPaging="Tr ue"
OnDataBound="Pr oducts_DataBoun d">
<Columns>
<asp:BoundFie ld DataField="Prod uctName" HeaderText="Pro duct
Name" SortExpression= "ProductNam e" />
<asp:BoundFie ld DataField="Cate goryName"
HeaderText="Cat egory" ReadOnly="True" SortExpression= "CategoryNa me" />
<asp:BoundFie ld DataField="Supp lierName"
HeaderText="Sup plier" ReadOnly="True" SortExpression= "SupplierNa me" />
<asp:BoundFie ld DataField="Unit Price" HeaderText="Pri ce"
SortExpression= "UnitPrice" />
<asp:CheckBoxFi eld DataField="Disc ontinued"
HeaderText="Dis continued" SortExpression= "Discontinu ed" />
</Columns>
</asp:GridView>
<asp:ObjectData Source ID="ObjectDataS ource1" runat="server"
OldValuesParame terFormatString ="original_{ 0}"
SelectMethod="G etProducts"
TypeName="Produ ctsBLL"></asp:ObjectDataS ource>
</asp:Content>
---------------

-----logic----
using System;
using System.Data;
using System.Configur ation;
using System.Collecti ons;
using System.Web;
using System.Web.Secu rity;
using System.Web.UI;
using System.Web.UI.W ebControls;
using System.Web.UI.W ebControls.WebP arts;
using System.Web.UI.H tmlControls;

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

protected void Products_DataBo und(object sender, EventArgs e)
{
PageInfo.Text = string.Format(" Page {0}/{1}",
Products.PageIn dex + 1, Products.PageCo unt);

PageList.Items. Clear();

for (int i = 0; i < Products.PageCo unt; i++)
{
ListItem pageListItem = new ListItem(string .Concat("Go to
page: ", i + 1), i.ToString());
PageList.Items. Add(pageListIte m);

if (i == Products.PageIn dex)
pageListItem.Se lected = true;
}
}

protected void PageList_Select edIndexChanged( object sender,
EventArgs e)
{
Products.PageIn dex = Convert.ToInt32 (PageList.Selec tedValue);
}
}
---------------

--
Thanks in advance
Damien

[Mark Rae]

"Damien" <no************ **@recursor.net wrote in message
news:11******** **************@ m58g2000cwm.goo glegroups.com.. .

I'm trying to learn ASP.NET and got a problem with DroDownList...
SelectedIndexCh anged doesn't fire.
Maybe you'll be able to suggest something.

I think it may be connected with the fact I fill this list dynamically.

Hmm - well, you specify AutoEventWireup ="true" in your Page directive, and
you have set the AutoPostBack property of the DropDownList control to
"true", so it can't be either of those...

protected void PageList_Select edIndexChanged( object sender, EventArgs e)
{
Products.PageIn dex = Convert.ToInt32 (PageList.Selec tedValue);
}
}

Are you absolutely certain the event isn't firing...? E.g. if you put a
breakpoint in the above code, does it jump into it...?

When you drop the DropDownList control and select a different option, does
the screen "flash" is if it's posting back...?

[Damien]

Are you absolutely certain the event isn't firing...? E.g. if you put a breakpoint in the above code, does it jump into it...?

I'm sure. I put breakpoint inside the event but it is never reached.

When you drop the DropDownList control and select a different option, does the screen "flash" is if it's posting back...?

Yes, the screen "flash", so page is posting back.

Another strange thing is when I add another dropdownlist to the form,
then add a few items to it... its SelectedIndexCh anged event fires no
matter which dropdownlist I use to select value.

The same event for both DDL... how is it possible?

[Mark Rae]

"Damien" <no************ **@recursor.net wrote in message
news:11******** *************@q 2g2000cwa.googl egroups.com...

>Are you absolutely certain the event isn't firing...? E.g. if you put a
breakpoint in the above code, does it jump into it...?

I'm sure. I put breakpoint inside the event but it is never reached.

Hmm - OK...

>When you drop the DropDownList control and select a different option,
does the screen "flash" is if it's posting back...?

Yes, the screen "flash", so page is posting back.

Well that's a start, at least... :-)

Another strange thing is when I add another dropdownlist to the form,
then add a few items to it... its SelectedIndexCh anged event fires no
matter which dropdownlist I use to select value.

Ah yes, now this is a particularly irritating bug...

The only way I've found of working round this is to wrap the entire code
inside the DropDownList's SelectedIndexCh anged event with this:

if (Request.Form["__EVENTTAR GET"] == PageList.Unique ID)
{
// rest of code goes here
}

The event still fires in response to postbacks from other controls, but none
of its code will run unless the actual DropDownList itself initiated the
postback...

I'm actually quite pleased that you're experiencing this (if you see what I
mean!), because Microsoft Technical Support as well as a couple of the MVPs
in here flatly refuse to acknowledge that this bug exists...

[Damien]

Thank for the clue (good one).
I will try this. However I think there is something wrong with the
following code:

--
//clear out all of the items
PageList.Items. Clear();

for (int i = 0; i < Products.PageCo unt; i++)
{
ListItem pageListItem = new ListItem(string .Concat("Page ", i + 1),
i.ToString());
PageList.Items. Add(pageListIte m);

if (i == Products.PageIn dex) pageListItem.Se lected = true;
}
--

If I add DDL items in VS environment, everything works fine.

Maybe, if I find out what is wrong with the above fragment, the event
problem will solve automatically.
MS products amaze me all the time, you know :)

--
Thanks a lot
Damien

[Mark Rae]

"Damien" <no************ **@recursor.net wrote in message
news:11******** *************@v 33g2000cwv.goog legroups.com...

However I think there is something wrong with the following code:

Like what...?

--
//clear out all of the items
PageList.Items. Clear();

for (int i = 0; i < Products.PageCo unt; i++)
{
ListItem pageListItem = new ListItem(string .Concat("Page ", i + 1),
i.ToString());
PageList.Items. Add(pageListIte m);

if (i == Products.PageIn dex) pageListItem.Se lected = true;
}
--

The only thing I might have done differently would be to evaluate whether
the item should be selected *before* adding it to the Items collection, e.g.

if (i == Products.PageIn dex) pageListItem.Se lected = true;
PageList.Items. Add(pageListIte m);

[Damien]

>However I think there is something wrong with the following code:

>Like what...?

No idea. But all works just fine when I create all items by hand.
Maybe I should place this code within different event. I'll work on
this.

>--
//clear out all of the items
PageList.Items .Clear();
for (int i = 0; i < Products.PageCo unt; i++)
{
ListItem pageListItem = new ListItem(string .Concat("Page ", i + 1),
i.ToString() );

PageList.Items. Add(pageListIte m);

> if (i == Products.PageIn dex) pageListItem.Se lected = true;
}
--

The only thing I might have done differently would be to evaluate whether
the item should be selected *before* adding it to the Items collection, e.g.

if (i == Products.PageIn dex) pageListItem.Se lected = true;
PageList.Items. Add(pageListIte m);

Any particular reason why?

[Mark Rae]

"Damien" <no************ **@recursor.net wrote in message
news:11******** *************@k 78g2000cwa.goog legroups.com...

>The only thing I might have done differently would be to evaluate whether
the item should be selected *before* adding it to the Items collection,
e.g.

if (i == Products.PageIn dex) pageListItem.Se lected = true;
PageList.Items .Add(pageListIt em);

Any particular reason why?

Force of habit, really...

1) Instantiate the object
2) Populate its properties
3) Add it to the collection