I have two dropdownlists, the first is populated with a fixed
collection, and the second has no listitems. When the first dropdown
is selected the second one will populate accordingly. Is there a way
that I can have the list items in the second dropdown populate without
using an auto postback? Thank you

Yes, you will have to use JavaScript, or AJAX.

can u please tell me the code using javascript....

No I can't. Try posting in a JavaScript forum, the would be better to help you there.

k.madhu

I had such a scenario once. I can't give you the code it self because I don't have it :), but concept is simple;

If you are using JavaScript, you need to create an HTML Hidden field, and store the values at it and then copy it back at the second drop down list (or listbox if you where using one).

But I really recommend using AJAX, it's a good practice, and you can find some good free assemblies which can help you, me my self I really like "Anthym" it's very simple yet powerful, anyway with AJAX I don't think you'll have any problem :)


Nothing is impossible. The impossible only takes longer. "Digital Fortress, Dan Brown"

Hi,

I'm just curious. I use muliple drop-downs extensively in my applications that fire on SelectedIndexChanged. They work soooo fine. I used to do those with Javascript. What a pain! Why can't you tolerate the postback?

Thanks,
Richard

Well it really depends on your application, if it's published on the internet, or if the amount of data posted into the page is relatively huge, I believe you should minimize the amount of data posted from/to the server, and the amount of the server trips too.

But if it's and internal web application, that is published in an internal LAN, well.. yeah I agree, why bother :).

But anyway it's always a good practice to try new stuff, thats why we have choosen this field of studying for after all :D


Nothing is impossible. The impossible only takes longer. "Digital Fortress, Dan Brown"

If you don't want to send a lot of data to the client then the javascript solution is the worst since it will send out all of the data at once to the client for all of the options in the first drop-down. In the javascript solution all of the data exists on the page and then is accessed whenever you change the selection in the first drop-down. And it can be extremely messy.

I'll send some example code if you're still interested... and I can still find some of my own since the autopostback and SelectedIndexChange have been a God send for me. However, I have never tried to integrate that javascript into a .NET application.

Richard

yeah rstelma I agree with the messy part, JavaScript by nature is a very messy scripting language, but when you say:
 "If you don't want to send a lot of data to the client then the JavaScript solution is the worst since it will send out all of the data at once to the client for all of the options in the first drop-down", I really disagree :), although it's true you send some extra script when using a JavaScript, but that this data is sent only when you inquire the page, after that, as you said, all the work is processed on the client machine, while if you used "autoPostBack", every time you do the even (change the index in our case) you'll do a server trip, which is an extra load on the server, specially if you are inquiring a huge amount of data from a database and sending it through the internet, it will be like hell to you customer to wait for the page :)

Nothing is impossible. The impossible only takes longer. "Digital Fortress, Dan Brown"