>Hi Tim,
>
>The biggest one has about 5k records. Some of them may be processed, depends on which control causes the postback. Most of them are binding to a table, and I found that the slow is caused by the rendering of the control.
>
>I'm thinking to create a custom popup to replace all the dropdownlist with binding to data, is that a better approach?

You're going to find that displaying 5000 records is going to be slow no matter how you decide to display them (eg. either via a dropdown, or pop-up in a new form). Ignoring the amount of data being sent to the browser, browsers generally choke on rendering that many records. Even 400-500 records can be too many. In most cases some sort of search to find/limit the results is the only way to handle this; you could even use some sort of AJAX-style incremental search (similar to what Google does) if you're search is quick enough. Or, page the data.