怎么解决这个问题？win 7的
下面是源代码：
using System;
using System.Collections.Generic;
using System.Text;
using System.Data.SqlClient;
namespace ConsoleApplication1
{
     class Program
     {
         static void Main(string[] args)
         {
             string myConnectionString = "Initial Catalog=Northwind;Data Source=localhost;Integrated Security=SSPI;";
             SqlConnection myConnection = new SqlConnection(myConnectionString);
             myConnection.Open();
             string s = "数据库状态：" + myConnection.State.ToString();
             Console.WriteLine(s);
             myConnection.Close();
             Console.ReadKey();
         }
     }
}
未处理的异常:   System.Data.SqlClient.SqlException: 无法打开登录所请求的数据库 "N
orthwind"。登录失败。
用户 'twpc-PC\twpc' 登录失败。