How to specify Entity Framework Code First connection string in external Enterprise Library config file

Question

I am creating a WPF application, having classical architecture: UI layer, business logic layer and infrastructure layer. I decided to split configuration in two files: app.config file, containing common app configuration, and dll.config, containing connection string to use in DbContext for domain model storage. The second .config file should be sticked to business logic DLL, while first file sticked to corresponding UI executable (there will be one more UI with it's own configuration).

app.config:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="enterpriseLibrary.ConfigurationSource" type="Microsoft.Practices.EnterpriseLibrary.Common.Configuration.ConfigurationSourceSection, Microsoft.Practices.EnterpriseLibrary.Common, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="true" />
  </configSections>

  <enterpriseLibrary.ConfigurationSource selectedSource="Winter DAL Configuration">
    <sources>
      <add name="Winter DAL Configuration" type="Microsoft.Practices.EnterpriseLibrary.Common.Configuration.FileConfigurationSource, Microsoft.Practices.EnterpriseLibrary.Common, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
        filePath="dll.config" />
    </sources>
  </enterpriseLibrary.ConfigurationSource> 
</configuration>

dll.config:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="dataConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Data.Configuration.DatabaseSettings, Microsoft.Practices.EnterpriseLibrary.Data, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="true" />
  </configSections>
  <dataConfiguration defaultDatabase="WinterContext" />
  <connectionStrings>
    <add name="WinterContext" connectionString="Data Source=Winter.sdf"
      providerName="System.Data.SqlServerCe.4.0" />
  </connectionStrings>
</configuration>

Now, when I'm starting the app, DbContext throws an exception saying it cannot find connection string with specified name. If I move connection string from dll.config to app.config - all working fine.

Maybe I must explicitly load configuration somehow? Or?.. What do I do wrong?

Thx in advance!

Answer 1

Based on the config files supplied, Entity Framework went looking in app.config of root in start project and didnt find the EF content. Especially the Connection string. When you first used UF it would have created such entries, perhaps in the model project. IM using EF5.0 so careful with cut and paste on Entity Section .

<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=5.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
</configSections>
<startup>
  <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
</startup>
<entityFramework>
 <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
   <parameters>
     <parameter value="v11.0" />
   </parameters>
 </defaultConnectionFactory>
</entityFramework>
<connectionStrings>

<add name="CONTEXT_NAME_HERE"
     providerName="System.Data.SqlClient"
     connectionString="Data Source=YOURDB_SERVER;Initial Catalog=YOUR_DBNAME;Integrated Security=True;MultipleActiveResultSets=True;App=EntityFramework" />

</connectionStrings>
</configuration>

Answer 2

I hope I understood your question, you want to structure your app.configs as a hierarchy, which is valid, in web applications that is very common, the easiest way to let .net help you with the merging is specifiying the regions of app.config in all those configurations that need to be bounded, and in the inner configurations you can override the values until you have the last one, for example:

ROOT APPCONFIG

<configuration>
<commonCollection>
    <add key="first"  value="1" />
    <add key="second" value="2" />
    <add key="third"  value="3" />
</commonCollection>
</configuration>

INNER APPCONFIG

<configuration>
<commonCollection>
    <remove key="first" />        
    <add key="first"  value="10" />
</commonCollection>
</configuration>

Results:

ROOT APPCONFIG

first : 1
second: 2
third: 3

INNER APPCONFIG

first: 10
second: 2
third: 3

EDIT

for your EF context, to set the connection string in the constructor :

 public MyContextDB() :base("name=DefaultConnection")
 {
 //other initializers
 }

hope it helps,