title: How to validate a duplicate value of textbox in asp.net while submit button
body: <p>I have 3 text box's and a submit button when i enter the values and submit then values are entered in database .</p>
  
  <p>but when i enter the same values and enter then those values are also entered.......This should not happen...I need a popup window showing there are duplicate values that you have entered.Please give the code for aspx and aspx.cs and data base. Please explain in breif</p>