Ошибка "A network-related or instance-specific error occurred while establishing a connection to SQL Server"

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using DomainModel.Concrete;
using DomainModel.Abstract;
using System.Data.Linq.Mapping;
using DomainModel.Entities;
using WebUI.Models;
 
 
namespace WebUI.Controllers
{
    public class BooksController : Controller
    {
        private IBooksRepository booksRepository;
        public int PageSize = 4; 
        public BooksController(IBooksRepository booksRepository)
 
        {
           // string connString = @"Server=.;Database=BooksStore1;Trusted_Connection=yes;";
           // booksRepository = new SqlBooksRepository(connString);
            this.booksRepository = booksRepository;
        }
        public ViewResult List(int page)
        {
            return View(booksRepository.Books.Skip((page - 1) * PageSize).Take(PageSize).ToList());
        }
 
 
    }
}