MVC4－－工厂模式错误，帮忙解决一下。
项目结构：

错误截图：



web.config中已经设置
    <appSettings>
      <add key="DALPath" value="Zjgcxx.EFDAL" />
      <add key="HZ" value="DAL" />
  </appSettings>

各项目之间该引用的都已引用，部份代码如下：
DALFacotry.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Reflection;

using System.Text;



namespace Zjgcxx.DALFactory

{

    public class DALFactory

    {

        public static readonly string DALPath = System.Configuration.ConfigurationSettings.AppSettings["DALPath"];

        public static readonly string DALHZ = System.Configuration.ConfigurationSettings.AppSettings["HZ"];



        

        /// <summary>

        /// 创建实例

        /// </summary>

        /// <param name="assemblyPath"></param>

        /// <param name="objType"></param>

        /// <returns></returns>

        public static object CreateDAL(string assemblyPath, string objType)

        {

            var cacheDAL = DALCache.GetDAL(objType);

            if (cacheDAL == null)

            {

                cacheDAL = Assembly.Load(assemblyPath).CreateInstance(objType); //此句提示出错

                DALCache.SaveDAL(objType, cacheDAL);

            }

            return cacheDAL;

        }



    }

}

Web_userDALFactory.cs

using System;

using Zjgcxx.IDAL;



namespace Zjgcxx.DALFactory

{

    public class Web_userDALFactory : DALFactory

    {

        /// <summary>

        /// 获取 Web_user 的具体实例

        /// </summary>

        /// <returns></returns>

        public static IWeb_userDAL Create()

        {

            //从配置中获取 sql、oracle 还是 EF&nbs