The tag has two childtags - the Content Template and the Triggers tags.The Content Template tag is required, since it holds the content of the panel.I would really recommend you look into an update Panel before going this route, however. And if multiple are selected the browser posts it the values as a csv.c, you don't need to keep the selected items in a hidden field, if you make the select box runat="server" you can read the posted back value from Request. Note the items and selectedindex properties of the control will be wrong on the server since you've modified the itrmlist on the client which the server doesn't know about. What worked for me was to set Enable View State="false" for the Repeater.If in another situation, where there are only 2 update panels, and one will set off another one, then “Always” should be applied.One good example would be that there is a modal form for adding a new record which is in one update panel, and in another update panel there is a search grid which displays all records, both has the value of always set in the value, this will cause an refresh in the search grid update panel, which updates the grid with the new value.
I reloaded a dropdownlist in the pageload, and so the framework lost control of the items (the new ones) in the ddl, and the one i clicked (which didn't exist anymore) in a page.
Update panel is probably one of the first thing that you will use once you get your Ajax toolkit with the Framework.
Other than the basic button in the panel, I’ve just recently found a few other ways of triggering an refresh in the panel,which wasn’t obvious to me before.
Postback is triggered only when a user clicks 'OK' button.
Clicking 'Cancel' or outside the control collapses the drop down and restores the check box selection prior to opening the control.
In this post I'll give more details about the Drop Down Check Boxes control.