Everything is straightforward and no different from using controls inherited from - in this case no 'OK/Cancel' buttons are displayed in the bottom of the drop down box, no postback occurs when a user clicks outside control and drop down gets hidden.The server side event will be fired (if there's a handler specified) during postback from any other control from the page (in case selection change is detected). NET controls with value doesn't matter) - in this case there're action buttons displayed in the bottom of the drop down box.“Conditional” means that this update panel is not updated by updates done to other update panels.Using this method, if there are multiple update panels on the page, and you only want to update one panel not the other ones, then all update panels should be set with the render mode of “Conditional”.Then, of course, you have to split that again on the server and do something with your items, since your select is empty now that it's back on the server.All in all it's a pretty cumbersome solution that I would not really recommend, but if you really have to do client-side modifications of a list Box, it does work.The page contains a drop down check boxes for selecting years and a panel bellow which displays checked items whenever a postback from the control occurs (code for other controls from the picture was cut above): From the example we see that a control event is assigned and the page load handler performs data binding for the control.Whenever a user clicks 'OK' button in the drop down list a postback goes to server and panel in the bottom of the page is filled with all checked items.
In one example, there is a grid display a list of vehicles, on the right side of the grid, we want to display the details of the vehicle when a person clicks an item in the grid, but we want to do this so the page does not refresh.
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.
When the page renders on the client you can populate it from a split of your text field contents.
Then, when you are ready to post it, you repopulate the hidden field's contents from your modified .