SQL Server数据库编写通用数据访问方法(6)

using System;
using System.Data;
using System.Data.Common;
using System.Data.OleDb;  
using System.Configuration;    
using Common;

namespace DAL
{
   public class CustomersData : IDbCustomers
   {
public DataTable GetCustomers()
{
   string ConnectionString = 
ConfigurationSettings.AppSettings
["ConnectionString"];

   using (OleDbConnection cnn = new OleDbConnection
(ConnectionString))
   {
string cmdString = "SELECT CustomerID," +
   "CompanyName,ContactName " +
   "FROM Customers";

OleDbCommand cmd = 
   new OleDbCommand (cmdString, cnn);

OleDbDataAdapter da = new 
   OleDbDataAdapter(cmd); 

DataTable dt = new DataTable("Customers");

da.Fill(dt); 

return dt;
   }
}
public DataTable GetCustomerOrders(string CustomerID)
{
   // 待定
   return null;
}
public DataTable GetCustomersByCountry
   (string CountryCode)
{
   // 待定
   return null;
}
public bool InsertCustomer()
{
   // 待定
   return false;
}
   }
}

using System;
using System.Data; 

namespace Common
{
    public interface IDbCustomers
    {
  DataTable GetCustomers();
  DataTable GetCustomerOrders(string CustomerID);
  DataTable GetCustomersByCountry(string CountryCode);
  bool InsertCustomer();
    }
}