"One size fits all" solution for freezing a Grid's header rows, why not?

using System;
using System.Data;
using System.Data.SqlClient;
using System.Collections.Generic;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;

/// <summary>
/// Summary description for DataProvider
/// </summary>
public class DataProvider : IDisposable
{
    private string _connectionString = "";
    /// <summary>
    /// Error reading from the database
    /// </summary>
    private bool _error;

	public DataProvider()
	{
        _connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["NorthwindSqlServer"].ConnectionString;
	}

    public object GetCustomers()
    {
        using (SqlConnection connection = new SqlConnection(_connectionString))
        {
            connection.Open();
            string queryString = "SELECT CustomerID, ContactName, ContactTitle, Address, CompanyName, Phone, Fax FROM Customers";
            SqlCommand command = new SqlCommand(queryString, connection);
            //SqlDataReader reader = command.ExecuteReader();
            SqlDataAdapter adapter = new SqlDataAdapter(command);
            DataSet ds = new DataSet();
            adapter.Fill(ds);
            //object result = reader;
            connection.Close();
            //reader.Close();
            return ds;
        }
    }

//    public object GetOrders(DateTime from, DateTime to)
//    {
//        _error = false;

//        try
//        {
//            using (SqlConnection connection = new SqlConnection(_connectionString))
//            {
//                connection.Open();
//                string queryString = @"SELECT o.OrderID, c.ContactName as CustomerName, o.OrderDate, o.ShippedDate, o.ShipAddress FROM Orders o 
//                INNER JOIN Customers c ON (o.CustomerID = c.CustomerID) where datediff(day, @from, OrderDate) >=0 and datediff(day, @to, OrderDate) <=0";

//                SqlCommand command = new SqlCommand(queryString, connection);

//                SqlParameter para1 = new SqlParameter("@from", SqlDbType.DateTime);
//                SqlParameter para2 = new SqlParameter("@to", SqlDbType.DateTime);

//                if (from == DateTime.MinValue)
//                    para1.Value = System.Data.SqlTypes.SqlDateTime.MinValue.Value;
//                else
//                    para1.Value = new System.Data.SqlTypes.SqlDateTime(from);

//                if (to == DateTime.MinValue)
//                    para2.Value = System.Data.SqlTypes.SqlDateTime.MaxValue.Value;
//                else
//                    para2.Value = to;

//                command.Parameters.Add(para1);
//                command.Parameters.Add(para2);
                
//                IDataReader reader = command.ExecuteReader();
//                List<Order> objOrders = new List<Order>();

//                while (reader.Read())
//                {
//                    Order objOrder = new Order();

//                    objOrder.OrderID = (int)reader["OrderID"];
//                    objOrder.CustomerName = (string)reader["CustomerName"];
//                    //objOrder.OrderDate = (DateTime)reader["OrderDate"];
//                    if (reader["OrderDate"] != DBNull.Value)
//                        objOrder.OrderDate = (DateTime)reader["OrderDate"];
//                    else
//                        objOrder.OrderDate = null;

//                    //objOrder.ShippedDate = (reader["ShippedDate"] == DBNull.Value?null:(DateTime)reader["ShippedDate"]);

//                    if (reader["ShippedDate"] != DBNull.Value)
//                        objOrder.ShippedDate = (DateTime)reader["ShippedDate"];
//                    else
//                        objOrder.ShippedDate = null;

//                    objOrder.ShipAddress = (string)reader["ShipAddress"];

//                    objOrders.Add(objOrder);
//                }

//                return objOrders;
//            }
//        }
//        catch (System.Exception ex)
//        {
//            _error = true;
//            return null;
//        }
//    }
    public int SumOrderAmount(int orderID)
    {
        _error = false;

        try
        {
            using (SqlConnection connection = new SqlConnection(_connectionString))
            {
                connection.Open();
                string queryString = @"select SUM(d.UnitPrice * d.Quantity - d.Discount) as OrderAmount from [Order Details] d 
                                       where d.OrderID = @OrderID";

                SqlCommand command = new SqlCommand(queryString, connection);

                SqlParameter para = new SqlParameter("@OrderID", SqlDbType.Int);
                para.Value = orderID;

                command.Parameters.Add(para);

                return (int)Math.Round((double)command.ExecuteScalar());
            }
        }
        catch (System.Exception ex)
        {
            _error = true;
            Exception = ex.Message;
            return 0;
        }
    }

    public object GetOrders(DateTime from, DateTime to)
    {
        _error = false;

        try
        {
            using (SqlConnection connection = new SqlConnection(_connectionString))
            {
                connection.Open();
                string queryString = @"SELECT o.OrderID, c.ContactName as CustomerName, o.OrderDate, o.ShippedDate, o.ShipAddress FROM Orders o 
                INNER JOIN Customers c ON (o.CustomerID = c.CustomerID) where datediff(day, @from, OrderDate) >=0 and datediff(day, @to, OrderDate) <=0 order by OrderID Desc";

                SqlCommand command = new SqlCommand(queryString, connection);

                SqlParameter para1 = new SqlParameter("@from", SqlDbType.DateTime);
                SqlParameter para2 = new SqlParameter("@to", SqlDbType.DateTime);

                if (from == DateTime.MinValue)
                    para1.Value = System.Data.SqlTypes.SqlDateTime.MinValue.Value;
                else
                    para1.Value = new System.Data.SqlTypes.SqlDateTime(from);

                if (to == DateTime.MinValue)
                    para2.Value = System.Data.SqlTypes.SqlDateTime.MaxValue.Value;
                else
                    para2.Value = to;

                command.Parameters.Add(para1);
                command.Parameters.Add(para2);

                IDataReader reader = command.ExecuteReader();

                List<Order> objOrders = DataHelper.PopulateEntities<Order>(reader);

                return objOrders;
            }
        }
        catch (System.Exception ex)
        {
            _error = true;
            Exception = ex.Message;
            return null;
        }
    }

    public object GetOrderDetails(int paraOrderID)
    {
        _error = false;

        try
        {
            using (SqlConnection connection = new SqlConnection(_connectionString))
            {
                connection.Open();
                string queryString = @"SELECT p.ProductName, d.UnitPrice, d.Quantity, d.Discount FROM [Order Details] d 
                INNER JOIN Orders o ON (o.OrderID = d.OrderID) 
                INNER JOIN Products p ON (p.ProductID = d.ProductID) 
                WHERE d.OrderID = @OrderID";

                SqlCommand command = new SqlCommand(queryString, connection);

                SqlParameter para = new SqlParameter("@OrderID", SqlDbType.Int);
                para.Value = paraOrderID;

                command.Parameters.Add(para);

                IDataReader reader = command.ExecuteReader();
                List<OrderDetail> objOrderDetails = DataHelper.PopulateEntities<OrderDetail>(reader);

                return objOrderDetails;
            }
        }
        catch (System.Exception ex)
        {
            _error = true;
            Exception = ex.Message;
            return null;
        }
    }

    /// <summary>
    /// Indicates some error ocurred when getting data
    /// </summary>
    public bool Error { 
        get { return _error; } 
    }

    /// <summary>
    /// Indicates some error ocurred when getting data
    /// </summary>
    public string Exception
    {
        get;
        set;
    }

    #region IDisposable Members

    /// <summary>
    /// Releases resources used by this class
    /// </summary>
    public void Dispose()
    {
        GC.SuppressFinalize(this);
    }

    #endregion
}