ado.net 的通道打不开

static void Check()
        {
            string sqlStr = @"server=.\express;database=Book;Integrated Security=True";

            SqlConnection con = new SqlConnection(sqlStr);

            con.Open();

            con.Close();

            Console.WriteLine("Ok");
            Console.ReadKey();
        }
到了open这边就报错。实在找不到哪里做了。会不会是数据库本身的问题啊？