using System;
using System.Web;
using System.Web.Caching;
using System.Configuration;
using System.Data;
using System.Data.OleDb;
using NGuestBook.Utility;

namespace NGuestBook.AccessDAL
{
/**//// <summary>
/// Access數據庫操作助手
/// </summary>
public sealed class AccessDALHelper
{
/**//// <summary>
/// 讀取Access數據庫的連接字符串
/// 首先從緩存里讀取，如果不存在則到配置文件中讀取，并放入緩存
/// </summary>
/// <returns>Access數據庫的連接字符串</returns>
private static string GetConnectionString()
{
if (CacheAccess.GetFromCache("AccessConnectionString") != null)
{
return CacheAccess.GetFromCache("AccessConnectionString").ToString();
}
else
{
string dbPath = ConfigurationManager.AppSettings["AccessPath"];
string dbAbsolutePath = HttpContext.Current.Server.MapPath(dbPath);
string connectionString = ConfigurationManager.AppSettings["AccessConnectionString"];

CacheDependency fileDependency = new CacheDependency(HttpContext.Current.Server.MapPath("Web.Config"));
CacheAccess.SaveToCache("AccessConnectionString", connectionString.Replace("{DBPath}", dbAbsolutePath), fileDependency);

return connectionString.Replace("{DBPath}", dbAbsolutePath);
}
}

/**//// <summary>
/// 執行SQL語句并且不返回任何值
/// </summary>
/// <param name="SQLCommand">所執行的SQL命令</param>
/// <param name="parameters">參數集合</param>
public static void ExecuteSQLNonQuery(string SQLCommand,OleDbParameter[] parameters)
{
OleDbConnection connection = new OleDbConnection(GetConnectionString());
OleDbCommand command = new OleDbCommand(SQLCommand, connection);

for (int i = 0; i < parameters.Length; i )
{
command.Parameters.Add(parameters[i]);
}

connection.Open();
command.ExecuteNonQuery();
connection.Close();
}

/**//// <summary>
/// 執行SQL語句并返回包含查詢結果的DataReader
/// </summary>
/// <param name="SQLCommand">所執行的SQL命令</param>
/// <param name="parameters">參數集合</param>
/// <returns></returns>
public static OleDbDataReader ExecuteSQLDataReader(string SQLCommand,OleDbParameter[] parameters)
{
OleDbConnection connection = new OleDbConnection(GetConnectionString());
OleDbCommand command = new OleDbCommand(SQLCommand, connection);

for (int i = 0; i < parameters.Length; i )
{
command.Parameters.Add(parameters[i]);
}

connection.Open();
OleDbDataReader dataReader = command.ExecuteReader();
//connection.Close();

return dataReader;
}
}
}