Accessing checkboxlist from code-behind

guynorton · February 6th, 2011, 03:10 PM

I have a form with a checkboxlist:

<asp:CheckBoxList ID="cblGames" runat="server" DataSourceID="sqlGames" DataTextField="Game" DataValueField="Id" </asp:CheckBoxList>
<asp:SqlDataSource ID="sqlGames" runat="server" ConnectionString="<%$ ConnectionStrings:Games %>"

<SelectCommand="SELECT [Id], [Game], [ShowWaitingList] FROM [Aanbod] WHERE ([ShowWaitingList] = @ShowWaitingList)">
<SelectParameters><asp:Parameter DefaultValue="true" Name="ShowWaitingList" Type="Boolean" /></SelectParameters>
</asp:SqlDataSource>

The code-behind is supposed to check the boxes according to values read in from a database. It fails to do so because it doesn't find the checkboxlist. This list has an ID of cblGames in both the page and the code-behind. So what am I doing wrong?

Regards, Guy

Code:

if    (!Page.IsPostBack && Request.QueryString["id"] != null)
        {
               // Code that gets the data goes here. Removed for brevity's sake //
              ListItem currentCheckBox = cblGames.Items.FindByValue(reader["AanbodId"].ToString());
              if (currentCheckBox != null)
              {
                  currentCheckBox.Selected = true;
              }
             
            }

Imar · February 6th, 2011, 04:37 PM

Hi Guy,

Quote:

It fails to do so because it doesn't find the checkboxlist.

Does it not find the list? Or the item you're trying to find? In the former case, are you getting some sort of compilation error?

In the latter case, try binding the list explicitly:

Code:

 
cblGames.DataBind();
if (!Page.IsPostBack && Request.QueryString["id"] != null)

Hope this helps,

Imar

guynorton · February 6th, 2011, 05:55 PM

It doesn't find the list. No error thrown.

If I replace the list generated in the aspnet tag with another (same name of course) but with hardcoded values, it does find it!

I am at a loss here, regards, Guy

Imar · February 6th, 2011, 06:09 PM

But how then do you know it doesn't find the list?

Have you tried calling DataBind? My guess is the list is there, but empty.

Imar

guynorton · February 6th, 2011, 07:55 PM

The checkboxlist is outputted and functional (it passes values to a database insert on submit).

The dynamically generated list box outputs the following source to the browser:

HTML Code:

<table id="MainContent_cblGames">
	<tr>
		<td><input id="MainContent_cblGames_0" type="checkbox" name="ctl00$MainContent$cblGames$0" value="1" /><label for="MainContent_cblGames_0">2/2 NL Texas</label></td>
	</tr><tr>
		<td><input id="MainContent_cblGames_1" type="checkbox" name="ctl00$MainContent$cblGames$1" value="2" /><label for="MainContent_cblGames_1">2/4 NL Texas</label></td>
	</tr><tr>
		<td><input id="MainContent_cblGames_2" type="checkbox" name="ctl00$MainContent$cblGames$2" value="3" /><label for="MainContent_cblGames_2">5/5 NL Texas</label></td>
	</tr>
</table>

The hard-coded (set up with the same values as returned by the dynamically generated) listbox outputs the following code to the browser:

HTML Code:

<table id="MainContent_cblGames">
	<tr>
		<td><input id="MainContent_cblGames_0" type="checkbox" name="ctl00$MainContent$cblGames$0" value="1" /><label for="MainContent_cblGames_0">Text1</label></td>
	</tr><tr>
		<td><input id="MainContent_cblGames_1" type="checkbox" name="ctl00$MainContent$cblGames$1" value="2" /><label for="MainContent_cblGames_1">Text2</label></td>
	</tr><tr>
		<td><input id="MainContent_cblGames_2" type="checkbox" name="ctl00$MainContent$cblGames$2" value="3" /><label for="MainContent_cblGames_2">Text2</label></td>
	</tr>
</table>

The code behind routine checks boxes only for the hardcoded listview and not the dynamically generated listview. They both output the same html before the populate routine runs.

Can you spot something my weary mind can't?

regards, Guy

guynorton · February 6th, 2011, 09:24 PM

I've edited this post which originally stated the problem had somehow miraculously solved itself by trying it on a fresh install of windows (clutching at straws!). It hadn't.
I erroneously retried the version with the hardcoded checkbox list, which had always worked.
I cannot get the dynamically generated checklist boxes to populate from the code-behind.
I have no idea why...

Help!

guynorton · February 7th, 2011, 10:35 AM

Hi Imar,

I see you are located in Utrecht. That's almost close enough to hear my screams of frustration! I live close to Breda.

Are there any asp.net courses in this region suitable for 40 year olds who work fulltime irregular hours....

Learning this in a vacuum is too painstaking and slow....

Imar · February 7th, 2011, 12:05 PM

Ah, so that was you....

You can hire me through my company (http://devierkoeden.nl) for a personalized .NET training. Not cheap, but certainly worth it. I am also almost 40 and work irregular hours, so that shouln't be a problem ;-)

I don't know of any courses in your area but I know of some national training companies that can train you to become an ASP.NET TS (Technical Specialist) or MCP (Certified Professional). Not cheap either...

Cheers,

Imar

guynorton · February 7th, 2011, 01:34 PM

Hi Imar,

I'm not sure what 'not cheap' entails but for reasons of discretion won't ask on this forum. I'll be contacting you via 'De Vier Koeden'....

With respect to the problem that I've been banging my head up against these last few days I'll keep the values hard-coded for the meantime and press on. Who knows, maybe a flash of inspiration will hit me, to be preceded by a d'oh!

regards, Guy

Imar · February 7th, 2011, 01:49 PM

For the record: it's Koeden, not Koerden. E.g. animals, not people from Turkije, SyriÃ«, Irak, Iran and the former Sovjet Union;-)

Quote:

Can you spot something my weary mind can't?

I still think that by the time your code executes, the DropDownList does not contain any values yet. Then "the list can be found", but it doesn't contain any items which in turn means you can't set a selected item. Calling DataBind before you try to preselect an item should do the trick as then the SqlDataSource executes its code and the list gets populated.

Cheers,

Imar