如何使用.NET连接到SQL Server中的特定数据库

Question

下面连接数据库的代码，你能告诉我哪里弄错了吗？

   SqlConnectionStringBuilder setting = new SqlConnectionStringBuilder();
    setting.DataSource = ".\\SQLExpress";
    setting.InitialCatalog = "PCM_NEW";
  //  setting.UserInstance = true;
    setting.IntegratedSecurity = true;
    setting.AttachDBFilename = @"C:\Program Files\Microsoft SQL Server\MSSQL12.SQLEXPRESS\MSSQL\DATA\PCM_NEW.mdf";


    //setting.UserID = "LKALAY\\SQLEXPRESS";

    SqlConnection baglanti = new SqlConnection(setting.ConnectionString);
    return baglanti;

我收到错误：

  

错误：提供者：SQL网络接口，错误：26