using System;
using System.Reflection;
using System.Configuration;
using OT.IDAL;
namespace OT.DALFactory
{
    /// <summary>
    /// 抽象工廠模式創建DAL
    /// web.config 需要加入配置：（利用工程模式+反射機制+緩存機制，實現動態創建不同的數據層對象接口）
    /// DataCache類在導出代碼的檔案夾裏
    /// <appSettings> 
    /// <add key="DAL" value="OT.SQLServerDAL" />
    /// </appSettings> 
    /// </summary>
    public sealed class DataAccess
    {
        private static readonly string AssemblyPath = ConfigurationManager.AppSettings["DAL"];
        /// <summary>
        /// 創建對象或從緩存獲取
        /// </summary>
        public static T CreateObject<T>(string AssemblyPath, string ClassNamespace)
        {
            T objType = default(T);//= DataCache.GetCache(ClassNamespace);//從緩存讀取
            if (objType == null)
            {
                try
                {
                    objType = (T)Assembly.Load(AssemblyPath).CreateInstance(ClassNamespace);//反射創建
                    //DataCache.SetCache(ClassNamespace, objType);// 寫入緩存
                }
                catch
                { }
            }
            return objType;
        }

        /// <summary>
        /// 通過泛型實例化數據層接口
        /// </summary>
        /// <typeparam name="T">數據層接口對象</typeparam>
        /// <param name="ClassName">數據層名稱</param>
        /// <returns>數據層接口實例化對象</returns>
        public static T Create<T>(string ClassName)
        {
            string ClassNamespace = AssemblyPath + "." + ClassName;
            return CreateObject<T>(AssemblyPath, ClassNamespace);
        }

    }
}