Updating in database with textboxes

class PropagateAddsBuilder {
      static void Main() {
         string connString = "server=(local)\\SQLEXPRESS;database=MyDatabase;Integrated Security=SSPI";
         string qry = @"select * from employee";
 
         SqlConnection conn = new SqlConnection(connString);

         try {
            SqlDataAdapter da = new SqlDataAdapter();
            da.SelectCommand = new SqlCommand(qry, conn);

            SqlCommandBuilder cb = new SqlCommandBuilder(da);

            DataSet ds = new DataSet();   
            da.Fill(ds, "employee");

            DataTable dt = ds.Tables["employee"];

            // Add a row
            DataRow newRow = dt.NewRow();
            newRow["firstname"] = "y";
            newRow["lastname"] = "y";
            dt.Rows.Add(newRow);

            foreach (DataRow row in dt.Rows){
               Console.WriteLine(
                  "{0} {1}",
                  row["firstname"].ToString().PadRight(15),
                  row["lastname"].ToString().PadLeft(25));
            }

            da.Update(ds, "employee");
         } catch(Exception e)  {
            Console.WriteLine("Error: " + e);
         } finally {
            conn.Close();
         }
      }  
   }