支持SQL Server数据库又支持MongoDB数据库的数据访问设计

网站整体架构建议采用工厂模式

分别包括：数据访问层DAL，数据访问接口层IDAL，工厂层DALFactory，业务逻辑层，显示层这样的架构方式

在WebConfig配置采用何种数据库的数据访问层

 <appSettings>
 <add key="DAL" value="SQLServerDAL"/><!--数据访问层-->
</appSettings>

定义接口层

 public interface ILocal_TopicDAL
    {
        /// <summary>
        /// 根据问题ID获取问题详细
        /// </summary>
        /// <param name="LT_ID">问题ID</param>
        /// <returns></returns>
        Local_TopicModel getTopicById(int LT_ID, string sCityCode, string sLanguage);
}

数据访问层继承接口层

 public class Local_TopicDAL : ILocal_TopicDAL
    {
        #region 根据问题ID获取问题详细
        /// <summary>
        /// 根据问题ID获取问题详细
        /// </summary>
        /// <param name="LT_ID">问题ID</param>
        /// <param name="sCityCode">城市代码</param>
        /// <param name="sLanguage">语言</param>
        /// <returns></returns>
        public Local_TopicModel getTopicById(int LT_ID, string sCityCode, string sLanguage)
        {
            string sql = "select LT_ID,LT_Title,LT_ThanksInfo,LT_Content,LT_ViewCount,LT_CommentCount,LTC_ID,LT_UpdateDate,LT_LastReplyDate,"+
                "LT_Checked,isnull(LT_Status,0) as LT_Status,isnull(LM_ID,0) as LM_ID,LM_NickName,LT_IsEffectiveDate,LT_EffectiveDate,LT_CreateDate," +
                "LTT_ID"+
                ",LTK_IDs,LT_AboutIds"+
                " from Local_Topic"+
                " where LT_Checked=1 and LT_ID=@LT_ID";
            string ConnectionString = ConnectionManage.getConnectionString(sCityCode, sLanguage);//EdushiDataCenter.Current.CityConfigProvider.GetCitySetting(sCityCode, sLanguage).ECS_DBConnectString;
            SqlParameter[] parameters = { new SqlParameter("@LT_ID", SqlDbType.Int, 4) };
            parameters[0].Value = LT_ID;
            DataTable dt = DbHelperSQL.Query(sql, ConnectionString, parameters).Tables[0];
            if (dt.Rows.Count > 0)
            {
                return DatableToList.CreateItem<Local_TopicModel>(dt.Rows[0]);
            }
            else
            {
                return new Local_TopicModel();
            }
        }
        #endregion

工厂层根据DAL路径通过反射创建数据访问实例

private static readonly string AssemblyPath = ConfigurationManager.AppSettings["DAL"];//数据访问层的程序集

  #region 创建对象（不使用缓存）
        /// <summary>
        /// 创建对象（不使用缓存）
        /// </summary>
        /// <param name="AssemblyPath"></param>
        /// <param name="ClassNamespace"></param>
        /// <returns></returns>
        private object CreateObjectNoCache(string AssemblyPath, string ClassNamespace)
        {
            try
            {
                object objType = Assembly.Load(AssemblyPath).CreateInstance(ClassNamespace);
                return objType;
            }
            catch(Exception ex)
            {
                LogOperate.WriteErrorLog("创建反射异常（不使用缓存）", ex);
                return null;
            }
        }

业务逻辑层通过调用反射的数据访问实例来执行具体方法

#region 根据问题ID获取问题详细
        /// <summary>
        /// 根据问题ID获取问题详细
        /// </summary>
        /// <param name="LT_ID">问题ID</param>
        /// <returns></returns>
        public Local_TopicModel getTopicById(int LT_ID)
        {
            CacheConfigModel ccm = new CacheConfigHelper().getCacheConfigModelByCacheId(3, ConfigurationManager.AppSettings["sectionName"].ToString());
            string key = string.Format(ccm.CacheKey, _cityCode, LT_ID);
            object obj = cache.Get(key);
            if (obj == null)
            {
                object objType = new DataAccess().CreateObject("Local_TopicDAL");//创建Local_Topic的实例
                obj = objType == null ? new Local_TopicModel() : ((ILocal_TopicDAL)objType).getTopicById(LT_ID, _cityCode, _language);
                cache.Add(key, obj, DateTimeOffset.Now.AddSeconds(ccm.CacheTime));
            }
            return obj as Local_TopicModel;
        }
        #endregion