button event in datalist according to letter wise

actually I want to add A to Z button in my web page.and after clicking on any button,I want to show datalist record according to letter wise. For Example - If I click on A button ,I want to show every author name which first letter start with A,......If I I click On B,I want to show every author record which start with B .....as continue to Z .......I want to show every author name record which are saved in database according to letter