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Just read this article it is a very nice article written by Suthish  sir
http://www.c-sharpcorner.com/UploadFile/suthish_nair/3997/

Dear Pankaj

To creating like this stuff with help of two diff concept
1)  ajax  autocomplete extender

2)Jquery autocomplete plugin

here are some links for ajax  autocomplete extender :


http://blogs.msdn.com/b/brada/archive/2006/10/27/search-autocomplete-with-asp-net-ajax-extensions.aspx

http://www.codeproject.com/KB/ajax/autosuggestextender.aspx

http://omegacoder.com/?p=243

here are some links for ajax  autocomplete extender :

http://encosia.com/2008/03/27/using-jquery-to-consume-aspnet-json-web-services/

http://adammokan.wordpress.com/2009/11/04/jquery-autocomplete-plugin-with-asmx-web-service-and-json/

Check this article for a sample and do the remaining as per you required

http://www.highoncoding.com/Articles/595_Implementing_Auto_Suggest_Using_AutoCompleteExtender_Control.aspx