Как сделать средний поиск в выпадающем списке в ASP.NET?

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Hi, 
I want to do middle search option in my combo cox. How can i achieve this?
In <asp:dropdownlist> only have initial search not middle search.
Anyone help me. Thanks in advance.

Что я уже пробовал:

I tried dhtml combo. But its too slow for middle search.

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