AutoComplete.Net

AutoComplete.Net is a wrapper around the JQuery UI Autocomplete widget.
It makes it easier to add autocomplete functionalities without having to bother with tons of javascript.
Includes a WebControl for your Asp.Net web applications and a bunch of extension methods for your Asp.Net MVC web applications.
Their purpose is to provide developers with an easy interface to the cool JQuery UI autocomplete Widget.
It's developed in C#.

See Documentation: here