SQL Server数据库编写通用数据访问方法(4)

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

namespace DAL
{
   public class CustomersData
   {
public DataTable GetCustomers()
{
   string ConnectionString = 
ConfigurationSettings.AppSettings
["ConnectionString"];
   DatabaseType dbtype = 
(DatabaseType)Enum.Parse
(typeof(DatabaseType),
ConfigurationSettings.AppSettings
["DatabaseType"]);

   IDbConnection cnn = 
DataFactory.CreateConnection
(ConnectionString,dbtype);

   string cmdString = "SELECT CustomerID" +
",CompanyName,ContactName FROM Customers";

   IDbCommand cmd = 
DataFactory.CreateCommand(
cmdString, dbtype,cnn);

DbDataAdapter da = 
   DataFactory.CreateAdapter(cmd,dbtype); 

   DataTable dt = new DataTable("Customers");

   da.Fill(dt);

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