javascript problem aps.net

[pl]

1) create dropdown lists on server
2) manipulate on client using javascript
3) postback to server for processing and lost the
client side listbox changes made from javascript.
4) why?

defined js in page load:
cboInternalOrigin.Attributes.Add
("OnBlur", "CheckRequiredField()")

 

[Juan Wajnerman]

When the postback data is sent to the server, only
selected items for the list are sent, not the entire
collection of items. The server side control reads the
viewstate data to restore list items, and then receives
the postback data to set which items are selected.