Entity database connection error

First I am using Entity framework (first code). I created a context class with the following code.

public class ContactContext : DbContext
{
    public ContactContext()
        : base("DBConnectionString")
    {
        Database.SetInitializer<ContactContext>(new DropCreateDatabaseIfModelChanges<ContactContext>());
    }

    public DbSet<Contact> Contacts { get; set; }

}

      

        
        
        
      

    

Web.config file:

<add name="ContactMgrDBContext" connectionString="Data Source=(Local);Initial Catalog=ContactsDB;Integrated Security=SSPI;" providerName="System.Data.SqlClient"/>

      

        
        
        
      

    

Controller class:

public class ContactController : Controller
{

    ContactContext db = new ContactContext();

      

        
        
        
      

    

// // GET: / Contact /

    public JsonResult ContactList(int? selectedContact)
    {

        IQueryable<Contact> contacts = db.Contacts;

        //contacts.ToList()

        var contactsJson = JsonConvert.SerializeObject(contacts.ToList());

        return Json(contactsJson, JsonRequestBehavior.AllowGet);

}

      

        
        
        
      

    

When I run my application in debug mode, I get the following exception in this expression.

var contactsJson = JsonConvert.SerializeObject(contacts.ToList());

      

        
        
        
      

    

An exception of type "System.Data.ProviderIncompatibleException" occurred in EntityFramework.dll, but was not handled in user code Additional information: An error occurred while retrieving provider information from the database. It could be caused by Entity Framework using the wrong connection string. Check for internal exceptions and check if the connection string is correct.

Contact class code:

public class Contact
 {
    [Key]
    public int ContactId { get; set; }
    [Required, MaxLength(100)]
    public string FirstName { get; set; }
    [Required, MaxLength(100)]
    public string LastName { get; set; }
    public string EMail { get; set; }
    public string Phone { get; set; }
    public string BusinessName { get; set; }

 }