Add Eval to each of the textboxes that you want to bind with the data from datatable.
<asp:textbox id="txtBenid" enabled="false" runat="server" xmlns:asp="#unknown"></asp:textbox>
This is your code for the textbox in which you want id value to be binded.
Modify your code as:
<asp:textbox id="txtBenid" enabled="false" runat="server" xmlns:asp="#unknown">Text='<%# Eval("id") %>'></asp:textbox>
Similary add for other textboxes too.