ASPX Listbox AutoSelect

Question

3.00/5 (1 vote)

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ASP.NET

selection

ListBox

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Hello,

I need to know if there is a way in ASPX to auto select the first value in listbox,i've already tried to use

C#

ListBox_servidores.SelectedIndex = 0;
ListBox_servidores.Items[0].Selected = true;

but its not working, the first code selects the first item in the listbox, but at the same time when i try to use the selected item in another piece of code it looks like it is not selected.
The second code just returns an error :

SQL

Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

Regards
Thank You

Posted 29-May-12 3:25am

Member 8956437

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Comments

Ed Nutting 29-May-12 9:37am

Err I think I'm being a bit obvious here but the error is saying that you have tried to access index 0 of a list but it is out or range - i.e. your list is empty...Have you actually added items to your list?
Ed

Member 8956437 29-May-12 9:44am

Yes, i have 2 items in that list.

Ed Nutting 29-May-12 9:47am

Have you debugged it to make sure that there are two list items in it when the code runs? No items in the list would be the only thing that would cause : ListBox_servidores.Items[0] to throw the error you are getting.
Ed

Member 8956437 29-May-12 10:03am

I see what you mean, but when i open the web page i can see the items in the listbox, as you said, Listbox.items[0] should work correctly.

Member 8956437 29-May-12 10:09am

Unless.. im using a listbox with a datasource selected, so it can show the values from a database, and in the aspx.cs i wrote the code above, maybe it is running the code first and then running the datasouc to add the values to the listbox.

Ed Nutting 29-May-12 10:19am

Yes that makes some sense given that data loaders etc are supposed to use what's called lazy loading, only getting data when they really need to. You might want to research how to get the datasource to fill the list box immediately rather than waiting till the page renders.

Member 8956437 29-May-12 10:28am

yeah, that should fix the problem.

Member 8956437 29-May-12 10:41am

Instead of using the datasource, i did it all by code, it looks like its working correctly now.
Thanks Ed

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Sandeep Mewara · Accepted Answer · 2012-05-29T04:56:00

Solution 1

OP and Ed resolved the issue with comments!

Posting this to pop this one out of unanswered list.

Posted 29-May-12 4:56am

Sandeep Mewara