How do I reference configuration information from within multiple class libraries?

Question

I've got a bunch of DLL projects that I'm pulling into my application, each contains their own Settings.settings/app.config. When I compile the app and run for debugging, everything works just fine, but come deployment time I can't get my DLLs to read their own settings files.

I've been doing some reading and it has become apparent that there's a couple of methods to getting each dll to read its own configuration - one is to dedicate a .dll.config to the library and the other is to embed the dll's configuration in the process.exe.config.

I'm having significant issues trying to implement either and I wondered if anyone has any good docs on this - there appears to be a shortage on the Net.

I'd like a separate .dll.config for each of the libraries if possible, but in a pinch, getting each of my libraries to read their own section of the process.exe.config will do.

Can anyone point me in the right direction because I'm so close to rolling this application out but this stumbling block is causing me a significant headache.

Edit: When I merge the configuration files, I start getting TypeInitializer exceptions when I initialize objects withing my libraries. This is likely just me being retarded, but does someone have a working example of a merged config file and some basic demonstrative code for reading it from multiple assemblies?

Answer 1

Have each class library define configuration settings in a custom ConfigurationSection.

Then add custom section handlers to your process.exe.config file.

This MSDN article is pretty comprehensive in its explanation, with examples in both VB and C#.

Answer 2

What are the "significant issues" you encountered? I started with embedding the dll's config in the exe's config, which worked, but was cumbersome. I now have all the config stuff in one dll project. The only thing I needed to do to make that work (besides copying the settings over) was to change the Settings class to be public.

Here's an example of a merged app.config that works:

  <?xml version="1.0" encoding="utf-8" ?>
  <configuration>
    <configSections>
      <sectionGroup name="applicationSettings" type="System.Configuration.ApplicationSettingsGroup, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
        <section name="SharedConfig.Client.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
        <!-- Begin copy from library app.config -->
        <section name="SharedConfig.Library.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
        <!-- End copy from library app.config -->
      </sectionGroup>
    </configSections>
    <applicationSettings>
      <SharedConfig.Client.Properties.Settings>
        <setting name="Bar" serializeAs="String">
          <value>BarFromClient</value>
        </setting>
      </SharedConfig.Client.Properties.Settings>
      <!-- Begin copy from library app.config -->
      <SharedConfig.Library.Properties.Settings>
        <setting name="Bar" serializeAs="String">
          <value>BarFromLibrary</value>
        </setting>
      </SharedConfig.Library.Properties.Settings>
      <!-- End copy from library app.config -->
    </applicationSettings>
  </configuration>

Answer 3

See http://stackoverflow.com/questions/634439/if-app-config-for-a-dll-should-be-in-the-main-config-what-do-we-do-with-wcf-refe. The real answer is "copy and paste". That's unfortunately the general solution Microsoft had in mind. In some cases, the .NET 2.0 Settings mechanism can be used, as it bakes the default values into the DLL itself. At runtime, the DLL can then save updated settings - into the .exe.config.