c# - What is the way to populate a dropdownlist from a database in asp.net by using classes? -

i trying populate dropdownlist sql server using classes shown below. code breaks down when comes bind data dropdown list. gives error on giving dropdownlist datavaluefield , datattextfield.

html... a.aspx

<asp:dropdownlist id="nationalitydropdownlist" runat="server"  > </asp:dropdownlist> 

c#... a.aspx.cs

protected void page_load(object sender, eventargs e)     {         classes.nationality possiblenationality = new classes.nationality();         if (!page.ispostback)         {                           datatable datatable = possiblenationality.getnationality();             nationalitydropdownlist.datasource = datatable;              nationalitydropdownlist.datavaluefield = "id";             nationalitydropdownlist.datatextfield = "nationality";             nationalitydropdownlist.databind();         }     }  

nationality.cs

 public class nationality  {    public datatable getnationality()     {         sqlconnection conn;         sqlcommand comm;         string  connectionstring = configurationmanager.connectionstrings["informationconnection"].connectionstring;         conn = new sqlconnection(connectionstring);         comm = new sqlcommand("spgetallusers", conn);         comm.commandtype = commandtype.storedprocedure;         datatable datatable;         try         {             conn.open();             sqldataadapter da = new sqldataadapter();             da.selectcommand = comm;             datatable = new datatable();             da.fill(datatable);         }                 {             conn.close();         }         return datatable;     } } 

sql procedure....

alter procedure [dbo].[spgetnationalities]  begin     select * nationality; end 

this line of code in getnationalitymethod...

comm = new sqlcommand("spgetallusers", conn); 

...should instead

comm = new sqlcommand("spgetnationalities", conn); 

databinding should work if nationality table has columns id , nationality