Unable to retrive metadata

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MVC

How to solve following this problem.

When Create a Controller then error message show below is

Unable to retrive metadata for 'pos.Model.Semester'. Unable to cast objectof type
'System.Data.Entity.Core.Objects.ObjectContext' to type 'System.Data.Objects.ObjectContext'

Model Class is:

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;

namespace pos.Models
{
    public class Semester
    {
        [Key]
        public int SemesterId { get; set; }

        [Required]
        [MaxLength(30)]
        public string SemesterName { get; set; }
        public int Status { get; set; }
    }
}

Second Class is:

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Web;

namespace pos.Models
{
    public class SemesterContext : DbContext
    {
        public SemesterContext() : base("name=pos") { }
        public DbSet<Semester> Semesters { get; set; }
    }
}

And my Connection String is:

<connectionStrings>
   <add name="DefaultConnection" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=aspnet-pos-20150527182631;Integrated Security=SSPI;" providerName="System.Data.SqlClient" />

   <add name="pos" connectionString="Data Source=AZIZ;Initial Catalog=PointofSell;User ID=sa; Password=mdazizulhoque.bd1987" providerName="System.Data.SqlClient" />
  </connectionStrings>

please give me any idea how to solve this error.