Why has my ConnectionsStringCollection more entries than my connection-Strings section in app.config?

Question

In my C#-WinForms-application (.Net 3.5, VS2008) I read the App.Config using:

Configuration myConfig = 
  ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);

App.config contains two connection strings in the connectionStrings-Section:

<connectionStrings>
    <add name="db1" connectionString="connection1"
     providerName="System.Data.SqlClient"/>
    <add name="db2" connectionString="connection2"
      providerName="System.Data.SqlClient" />
</connectionStrings>

(connection strings abreviated for readability)

But when I loop through the ConnectionStringsCollection I find that it has three entries instead of the expected two. The additional entry points to a database called "aspnetdb.mdf" on a local SqlExpress-Server. I can't remember adding this anywhere, I can't find it as a literal value in my project files. Watching the collection with the debugger I find that my connection strings have the app.config as source. The additional string has null as source, so I think .net conjurs it up from somewhere.

How can I get rid of this entry, or failing that how can I tell the configuration manager to only use the connection strings in the app.config?

Answer 1

The aspnetdb.mdf comes from the default connection strings collection, remove it by adding

<clear />

to the top of your element.

Answer 2

Did you check machine.config?

(Found in %SystemRoot%\Microsoft.NET\Framework\v2.0.50727\CONFIG for 64bit use Framework64.)