Q:

how to postback part of a page in ASP.NET

I know that update panels help rendering part of a page, but what I'm asking is how to postback part of a page to server not all.  I have a page that has several inside each a form that postsback some info to server.  I want each submit button to postback only it's own form information not all others too. 
The actual problem is that when I submit one of the forms required field of other forms won't let me do the postback.  So a rephrased question might be, how do I disable validation for a button and enable it for others? 

A:

You need to use validation groups.   For example:
<asp:requiredfieldvalidator 
   ValidationGroup=“val_grp_1” 
   ErrorText=“Missing Value” 
   ControlToValidate=“txt_firstname” 
   runat=“server”/>

And then on your submit button, you reference the group you want to have validated:
<asp:button 
   text=“Group1” 
   ValidationGroup=“val_grp_1” 
   runat=“server”/>

