Filling Gridview Using value in text box without complete postback

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C#

ASP.NET

Javascript

SQL

Ajax

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I want to populate my grid view based on the values of a textbox. I want the contents of gridview to change with changing characters in textbox.
For Eg:

If value in textbox is 'a' all values starting with 'a' are shown in gridview and when the value is changed to 'ab' the grid content should change having only values starting with 'ab'.

Also i want to do this without complete postback as reloading the page is not an available option. I would like to do this using a javascript or axaj or jquery.
I m using C# with Asp.net 2010 and microsoft sql 2008 as the database