I’ve wanted to use dropdown lists in the advanced search property restrictions for a long time, so i created a web part to allow it (SearchExtension web part). It can be found on codeplex: http://spsearchextension.codeplex.com/
How it works:
- The events are triggered when the selected property changes, and cause the plain text box to be hidden, and a drop down list created and displayed in its place. The dropdowns created will pass their selected value to the orginal (hidden) text box which used to be there
- Dropdown list values are populated using callbacks from SharePoint lists or can be defined static (defined in the configuration XML of the SearchExtension web part)
- Two properties can be linked as parent/child – eg for “Category” / “Sub-category” scenarios
Please see the codeplex site for more information.