Error handling when inserting a null value, asp.net c# -

i have webpage built in asp.net c#. user create new record in db table. there there 2 input fields, text , score. text cannot null value if user doesn't input text onsubmit, page errors out. want throw in simple error handling code in code behind page. i've tried including if/else on_inserted method ran java script errors. apprieciated. thanks.

aspx page -----------------

 <edititemtemplate>                   <customeditors:editorwithcustombuttons_1 runat="server" id="editor1" content='<%# bind("usertext") %>' />                  </edititemtemplate>                 <insertitemtemplate>                   <customeditors:editorwithcustombuttons_1 runat="server" id="editor1" content='<%# bind("usertext") %>' />                 </insertitemtemplate> 

why not use requiredfieldvalidator validator? works inside grid