Autogenerated default connection string vs. manually added one

Question

Let's say I have got simple WPF application using Entity Framework Code First to create database, connect to it and display some data. From start I do not want to worry about connection strings so after adding entityframework reference via Nuget I'll get auto generated app.config looking like this:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  </configSections>
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework" />
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
      </providers>
  </entityFramework>
</configuration>

I'll run test and observe connection string:

var strings = ConfigurationManager.ConnectionStrings;

with result:

[0] = {data source=.\SQLEXPRESS;Integrated Security=SSPI;attachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true}

As I Like to define my own connection string, I will add this into my app.config:

<connectionStrings>
    <add name="MyContext" connectionString="data ource=(LocalDb)\v11.0;AttachDbFilename=|DataDirectory|\myDb.mdf;Integrated Security=True" providerName="System.Data.SqlClient" />
</connectionStrings>

And so when I run the test again and observe the connection srings I can see that there are two now:

[0] = {data source=.\SQLEXPRESS;Integrated Security=SSPI;attachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true}
[1] = {data source=(LocalDb)\v11.0;AttachDbFilename=|DataDirectory|\myDb.mdf;Integrated Security=True}

Why is it that I can see two connection string? If the first one is default, should it not be forgoten once I've created one?

Thanks

Answer 1

First connection string which you see comes from machine.config from your PC. It has following section:

<connectionStrings>
     <add name="LocalSqlServer" 
          connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true" 
          providerName="System.Data.SqlClient"/>
</connectionStrings>

Which defines default connection string for ASP.NET database. If you really don't need it for your application, you can either edit machine.config file (not recommended) or clear connection strings before adding yours:

<connectionStrings>
    <clear />
    <add name="MyContext" 
         connectionString="data source=(LocalDb)\v11.0;AttachDbFilename=|DataDirectory|\myDb.mdf;Integrated Security=True" 
         providerName="System.Data.SqlClient" />
</connectionStrings>

Also keep in mind - this connection string is not used by Entity Framework. By default it uses SQLEXPRESS server and database with name equal to full name of your DbContext class. You can check it by accessing context.Database.Connection.ConnectionString.

Answer 2

The configuration manager just grabs all of the connection strings defined in the app/web.config.

It can't make the generalized assumption that once you add a connection string you wouldn't want a default one around anymore. That second connection string might point to an entirely different database.