How do I pre-populate a frontend control using asp.net c#?

martinspalding · April 15th, 2010, 07:02 AM

My ItemDataBound event doesn't seem to fire? Do I have my query within the wrong event?

Thanks.

martinspalding · April 15th, 2010, 10:25 AM

Did you receive my last posts? I think the web site was down for a while.

Thanks.

Imar · April 15th, 2010, 04:50 PM

Take a look at this:

Traders myTraders = dataItem.DataItem as Traders;

Your DataItem is probably not a Traders instance. As such, the conversion fails, and myTraders remains null. This in turn means the control is never bound.

What do you see when you debug? That would be the way to figure these thing out. Because of the database dependency, I can't help much, other than tell you where to look for potential problems.

Cheers,

Imar

martinspalding · April 16th, 2010, 04:51 AM

That's my whole problem - I can't debug my ItemDataBound event as the error is occuring within my OnSelecting event, i.e. before my ItemDataBound event is fired. Can you think of any reason why your control would act this way bound to a linqdatasource instead of an objectdatasource? Thanks.

Imar · April 16th, 2010, 05:15 AM

You could try calling DataBind on your List or DataSource control manually in an earlier event, like Page_Load. Apparently when the control starts binding the life cycle is in Databinding mode and then my control does its checks.

Alternatively, you could remove the check in the control and not throw an error.

Again, since I don't have a reproducible scenario, I cannot test this for you. I also don't have the time to build a sample project and try to reproduce this for you. So, unless you send me a complete sample project, there's not much I can do for you.

Cheers,

Imar

martinspalding · April 16th, 2010, 06:03 AM

How would I remove the check in your control and not throw the error?

Thanks again.

Imar · April 16th, 2010, 06:21 AM

What about deleting the lines that do the check and throw the exception?

Not trying to be funny, but if you look at the code, it should be easy to see where this check is made and the error is thrown....

Imar

martinspalding · April 19th, 2010, 05:56 AM

Hi Imar,

I managed to delete the lines in your control that do the check and throw the exception but as predicted this led to other issues, i.e. within your RattingSettings class your rateItems variable is now null, which will be due to the fact that the ItemId cannot be found from the data source. Basically I cannot figure out a way to provide your control within my listview with an ItemId before I bind my listview, i.e. ContentRating1.DataSource must be bound before my listview has been bound but ContentRating1 requires the rating values returned from my listview's bound query - it's a bit of a catch 22!

Thanks.

Imar · April 20th, 2010, 05:09 AM

Like I said, I can't help you if you don't give me a reproducible and representable scenario. The C# example using classes was reproducible, but not representable.

I am sure this is all relatively easy to fix; it shouldn't take weeks. However, since I don't know what the problem is I can't fix it.

If you can, zip a fully working example (with just the files and tables needed) using your database schema, data, etc and either mail it to me or provide a download link somewhere. Then next week I'll be able to take look (on vacation now).

As I suggested earlier, did you try explicit binding in Page_Load? What happended when you try that?

Cheers,

Imar

martinspalding · April 20th, 2010, 06:57 AM

Imar,

Sorry I interrupted your vacation!

Unfortunately, I am already calling my Bind methods from my page load event.

If you find the time please navigate to the below address where you can download my ListView_Rating.zip file which holds my test web site. Simply extract and open the web site through VS 2008. You will have to have sql server 2008 express installed for it to work....

http://www.tradeselector.co.uk/Misc/ListView_Rating.zip

Thanks again.