The provider did not return a ProviderManifest Token String error in Asp.net MVC 3 Entity Framework?

Hi All,

Iam new to ASP.net MVC 3

iam using entity framework for connecting database.

but when iam creating controller it shows the following error

Unable to retrive Metadata for 'Entity.Models.student'.The provider did not return a ProviderManifest Token String

my student model class is:

public class student
    {
        public int sno { get; set; }
        public string  sname { get; set; }
        public int age { get; set; }
    }
    public class studentdbcontext : DbContext
    {
        public DbSet<student> ob { get; set; }
    }

my connection string is:

<add name="studentdbcontext"
connectionString="data source=localhost;Integrated Security=SSPI;database=demo;User ID=sa;password=12345"
providerName="System.Data.SqlClient"/>