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

namespace Example_11_14
{
	public enum DatabaseType
	{
		Access,
		SQLServer,
		Oracle
		// 任何其他數(shù)據(jù)源類型
	}

	public enum ParameterType
	{
		Integer,
		Char,
		VarChar
		// 定義公用參數(shù)類型集
	}

	public class DataFactory
	{
		private DataFactory(){}

		/// <summary>
		/// 創(chuàng)建訪問(wèn)數(shù)據(jù)庫(kù)的鏈接
		/// </summary>		
		public static IDbConnection CreateConnection(string ConnectionString,DatabaseType dbtype)
		{
			IDbConnection cnn;

			switch(dbtype)
			{
				///訪問(wèn)Access數(shù)據(jù)庫(kù)
				case DatabaseType.Access:
					cnn = new OleDbConnection(ConnectionString); 
					break;
			    ///訪問(wèn)SQL Server數(shù)據(jù)庫(kù)
				case DatabaseType.SQLServer:
					cnn = new SqlConnection(ConnectionString); 
					break;
			    ///訪問(wèn)Oracle數(shù)據(jù)庫(kù)
				case DatabaseType.Oracle:cnn = new OracleConnection
						(ConnectionString);
					break;
				///默認(rèn)訪問(wèn)SQL Server數(shù)據(jù)庫(kù)
				default:
					cnn = new SqlConnection(ConnectionString); 
					break;               
			}

			///返回訪問(wèn)數(shù)據(jù)庫(kù)的鏈接
			return cnn;
		}

		/// <summary>
		/// 創(chuàng)建訪問(wèn)數(shù)據(jù)庫(kù)的Command
		/// </summary>	
		public static IDbCommand CreateCommand(string CommandText, DatabaseType dbtype,
			IDbConnection cnn)
		{
			IDbCommand cmd;
			switch(dbtype)
			{
				///訪問(wèn)Access數(shù)據(jù)庫(kù)
				case DatabaseType.Access:
					cmd = new OleDbCommand(CommandText,(OleDbConnection)cnn);
					break;
				///訪問(wèn)SQL Server數(shù)據(jù)庫(kù)
				case DatabaseType.SQLServer:
					cmd = new SqlCommand(CommandText,(SqlConnection)cnn); 
					break;
                ///訪問(wèn)Oracle數(shù)據(jù)庫(kù)
				case DatabaseType.Oracle:
					cmd = new OracleCommand(CommandText,(OracleConnection)cnn);
					break;
				///默認(rèn)訪問(wèn)SQL Server數(shù)據(jù)庫(kù)
				default:
					cmd = new SqlCommand(CommandText,(SqlConnection)cnn); 
					break;
			}

			///返回訪問(wèn)數(shù)據(jù)庫(kù)的Command
			return cmd;
		}

		/// <summary>
		/// 創(chuàng)建訪問(wèn)數(shù)據(jù)庫(kù)的DataAdapter
		/// </summary>	
		public static DbDataAdapter CreateAdapter
			(IDbCommand cmd, DatabaseType dbtype)
		{
			DbDataAdapter da;
			switch(dbtype)
			{
					///訪問(wèn)Access數(shù)據(jù)庫(kù)
				case DatabaseType.Access:
					da = new OleDbDataAdapter
						((OleDbCommand)cmd); 
					break;

					///訪問(wèn)SQL Server數(shù)據(jù)庫(kù)
				case DatabaseType.SQLServer:
					da = new SqlDataAdapter
						((SqlCommand)cmd); 
					break;

					 ///訪問(wèn)Oracle數(shù)據(jù)庫(kù)
				case DatabaseType.Oracle:
					da = new OracleDataAdapter
						((OracleCommand)cmd); 
					break;

					///默認(rèn)訪問(wèn)SQL Server數(shù)據(jù)庫(kù)
				default:
					da = new SqlDataAdapter
						((SqlCommand)cmd); 
					break;
			}

			///返回訪問(wèn)數(shù)據(jù)庫(kù)的DataAdapter
			return da;
		}
	}

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

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


}