what's a good rule of thumb for max dropdown list options

with the title being self-explanatory enough, if you开发者_StackOverflow do reach this max number, what do you do instead?

thx :) -C

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Add a search box. This is what "StackOverflow" does:

alt text http://img689.imageshack.us/img689/6682/capturadepantalla200911y.png

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I'd recommend nothing higher than a common screen height, (say, 768 pixels) so the answer will depend on how many items you can fit in that space. After that I'd probably have a small list view that gives the user the ability to scroll through the options instead of requiring them to move their mouse to one extreme of the list or another and waiting until their option passes by. A search box would work as well, as long as the list was still browsable by other means.

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Anything over 10 items is probably "a lot" but not immediately too much, that all depends on the context of your application.

As for the second part of your question, you might have some success with the drill-down approach, where you have multiple methods of drilling down to a final choice, perhaps you can define groups in one dropdown and elements in the next, filling the second dropdown based on the coice made in the first.

Search can be a big help too, especially if done asynchronously (think AJAX) and the dropdown can be changed to a combobox.