title: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified for MDF file
body: <p>I have added a database file (<code>.mdf</code>) to my application using Visual Studio built-in functionality. Database is in the <code>App_Data</code> folder. It is running fine. But when I publish it and upload it to server it gives this error.</p>
  
  <blockquote>
    <p>A network-related or instance-specific error occurred while
    establishing a connection to SQL Server. The server was not found or
    was not accessible. Verify that the instance name is correct and that
    SQL Server is configured to allow remote connections. (provider: SQL
    Network Interfaces, error: 26 - Error Locating Server/Instance
    Specified)</p>
  </blockquote>
  
  <p>I visited similar situation but confused. I don't know which version and edition of SQL Server is running at server. I upload project using Filezilla. My connection string is as follows in my <code>web.config</code>:</p>
  
  <pre><code>&lt;add name="ConnectionString" 
       connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True" 
       providerName="System.Data.SqlClient"/&gt;
  </code></pre>
  
  <p>Please describe process step by step is possible.</p>
  
  <p>Thanks in advance.</p>