How to get distinct values of a managed property through SharePoint search?

I am building a phone catalog of my organization (an AJAX application which accesses the search.asmx web service). I'd like to show a list box where the user could select a department (which is stored in managed property Department). To fill the list box with values, I need to somehow select all the distinct values of that property. Is it possible through search.asmx web service?

What I've found:

• an article, which states that it is possible, but it does not use the web service interface
• a Microsoft's white paper which states that "If the protocol client specifies at least one property, it MUST also s开发者_Python百科pecify the Path property. If it does not, the protocol server MUST return the status code "ERROR_BAD_QUERY"."

The two findings are somewhat inconsistent. (and, yes the search really returns ERROR_BAD_QUERY).

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Why bother to check with the web service or complicate it?

1. Get all the properties into a DataTable.
2. Then create a DataView & then you can apply the DISTINCT on required column.
3. Finally use it to bind to your list box.