ObjectList Data-Binding to a List<MyClass>

[Guest]

Let's say I have defined a class:

public class TestClass
{
int m_ID;
string m_UserTitle;

public TestClass(int ID, string UserTitle)
{
m_ID = ID;
m_UserTitle = UserTitle;
}

public int ID
{
get
{
return (m_ID);
}
}
public string UserTitle
{
get
{
return (m_UserTitle);
}
}
}


Now I want to display it using an ObjectList, so I do this on my ASPX page...

<mobile:ObjectList ID="OL" Runat="server"
CommandStyle-StyleReference="subcommand" AutoGenerateFields="False"
LabelStyle-StyleReference="title">
<DeviceSpecific>
<Choice>
<ItemDetailsTemplate>
<mobile:Label ID="Label4" Runat="server"><%# Eval("ID")
%></mobile:Label>
<mobile:Label ID="Label2" Runat="server"><%#
Eval("UserTitle") %></mobile:Label>
<mobile:Image ID="Image2" Runat="server"

ImageUrl="http://www.asp.net/App_Themes/Standard/i/logo.png"></mobile:Image>
</ItemDetailsTemplate>
</Choice>
</DeviceSpecific>
</mobile:ObjectList>


NOW, back in my page code, I do this...

private void DisplayList()
{

List<TestClass> L = new List<TestClass>();

L.Add(new TestClass(1, "UserTitle 1"));
L.Add(new TestClass(2, "UserTitle 2"));

OL.DataSource = L;
OL.DataBind(); //RUNTIME ERROR HAPPENS HERE!
}

Note that I am trying to configure this control to only have one template
which will be very VERY simple and should work for all devices.

When I have done all this, I get a runtime error on the DataBind() line as
follows...

System.Exception was unhandled by user code
Message="Must have one or more fields to databind.
(Application may have autogenerated fields from an empty DataSource. To
clear items, set DataSource to null.)"


Any ideas what I'm doign wrong here?

Thanks!

Alex

 

[Steven Cheng[MSFT]]

Hi Alex,

Seems this is a continual post from a former thread discussing on "Mobile
Repeater", correct?

I've performed test through the code you provided and did met the error you
said. After some research, I found that the error is caused by no data
fields are defined in the ObjectList control. Actually, if you turn off
"AutoGenerateFields" in ObjectList, you need to supply the fields you want
to use in your ObjectList. You should use the <Field > element to add
fields definition into the ObjectList.

For your "TestClass" scenario, here is the expected ObjectList aspx
template:

================
<mobile:ObjectList ID="ObjectList1" Runat="server"
CommandStyle-StyleReference="subcommand"
LabelStyle-StyleReference="title" AutoGenerateFields="False"
LabelField="UserTitle" >

<DeviceSpecific ID="ds_ol1" Runat="server">

<Choice >



<ItemDetailsTemplate>
detail template:
<mobile:Label ID="Label1" Runat="server"><%# Eval("ID")
%></mobile:Label>
<mobile:Label ID="Label2" Runat="server"><%# Eval("UserTitle")
%></mobile:Label>

</ItemDetailsTemplate>

</Choice>

</DeviceSpecific>


<Field Title="ID" DataField="ID" />
<Field Title="UserTitle" DataField="UserTitle" />
</mobile:ObjectList>
========================

Also, I found a good web forum thread which has included some advanced
setting and usage upon ObjectList control, you can also have a look if you
need some further customzation or event handling:

http://forums.asp.net/p/1146753/1862202.aspx

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead



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[Guest]

Steven -

Thanks for getting back to me about all these posts. I have been away and am
just getting back to it now. I must say, I find this entire approach
*incredibly* complicated for something as simple as providing a listing of
objects/assets from a List or Database table. But there's nothing I can do
about it, I guess so I have to keep bothering you until I really understand.
I implemented exactly what you defined below and I'm no longer getting the
error I was getting before, but I *am* still having a problem:

In the <ItemDetailsTemplate> section (below), I've presented two
<mobile:Label ...> objects, one whose content is set to: <%# Eval("ID") %>
and another whose content is set to <%# Eval("UserTitle") %>. I then also
added the two <Field...> tags for ID and UserTitle below (just as you
defined). When I run this, though, all I see is a "table" with a single
column showing the "ID" header and "ID" entries only. The second label for
the "UserTitle" is simply not shown. Also, in your sample, you placed the
text "detail template:" just inside the <ItemDetailsTemplate> tag. This is
literal text and I would have assumed that it would just show up in every
row. Instead, it doesn't show up at all.

Can you please help? This is an incredibly complicated way of doing
something really simple - or so it seems.

Thanks as always.

Alex

 

[Guest]

Steven -

One more note: I have successfully gotton it to show both columns by adding
TableFields="ID;UserTitle"
to the <mobile:ObjectList...> tag. But I still can't get it to display
standard text of mark-up that I have placed in the <ItemDetailsTemplate>. It
just ignores that and only displays the <mobile: Label...> objects that I
have bound to my data fields. What is *with* this control?! Why is it so
constrained? All I want is a control that allows me to manually build HTML
markup for each object in a list (whether a database DataTable or some other
kind of list). I have that *so* easily with the Repeater control in standard
ASPX which allows me to repeat *anyuthing* over and over again based on rows
from a List. What that markup is that is sent to the browser is up to me and
if I include items that the browser can't handle, that's *my* problem. Why
can't I do that in mobile. Sorry, but this is incredibly frustrating for
something so simple.

As always, thanks!

Alex

 

[Steven Cheng[MSFT]]

Thanks for your followup Alex,

For the "ItemDetailsTemplate" template issue you mentioned, it maybe still
due to the control use the default template since there may have any other
setting and prevent your custom one from display. Yes, mobile control is
not natually targeting html from its designate, so that does make us feel
abit inconvenient when we want to author standard html/xhtml content for
mobile page.

BTW, as most smart devices not support html and asp.net standard
application control also have adaptable rendering model, maybe you can
consider use a standard aspx page here as you will mostly use html based
content. Is this possible in your application?


Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead


This posting is provided "AS IS" with no warranties, and confers no rights.


--------------------

Thread-Topic: ObjectList Data-Binding to a List<MyClass>
Date: Fri, 31 Aug 2007 07:52:01 -0700

 

[Guest]

Actually, the problem, it turns out, was that I was using
<ItemDetailsTemplate> when I should have been using <ItemTemplate>. When I
use that instead, the thing does what I need. I really appreciate all your
help. One suggestion: The whole ObjectList, DeviceSpecific, etc., etc.
business is, in my opinion, VERY poorly documented. Usually, you guys do a
really good job of definition, how-to, etc. In this area, the documentation
is really very poor.

In any case, I'm okay now. I really appreciate all your help.

Thanks.

Alex

 

[Steven Cheng[MSFT]]

Thanks for your followup Alex,

Yes, <ItemTemplate> will be displayed first, while <ItemDetailsTemplate> is
to displayed when a certain record is further choosen by the user. Anyway,
I'm glad that you've got the one you want.

For the document issue, I agree that the current samples and tutorials for
ASP.NET Mobile application are so limited. I think it is also probably due
to more users are focus on the standard web application developing. Anyway,
your comments and feedback is really appreicated and I suggest you submit
them to our feedback center:

https://connect.microsoft.com/feedback/default.aspx?SiteID=210&wa=wsignin1.0

You can also directly submit feedback through the web document page's
feedback button (on msdn2.microsoft.com....).

Thanks again for your posting and support to us!

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead


This posting is provided "AS IS" with no warranties, and confers no rights.



--------------------

Thread-Topic: ObjectList Data-Binding to a List<MyClass>
From: =?Utf-8?B?QWxleCBNYWdoZW4=?= <[email protected]>