I have a "business logic" dll that has a connectionString and some
my.mysettings.default values that I need to change based on the system
the dll is running on (i.e.: a development, test vs. a production
system).

So far, I've not been successful in getting the .dll to access
connectionStrings and other settings from the calling applications
web.config file (sample below).

1) How do I get a connectionString into a .dll at runtime (and
overwrite the "default" one compiled in)?
2) How do I get a my.mysettings.default setting into a .dll at runtime
(and overwrite the "default" one compiled in)?

The only thing that works below (in terms of accessing from the .dll)
is the "key" in the <appSettings> section - but that's going through
Configuration.ConfigurationManager.AppSettings(keyString), not
my.mysettings (which is OK, I guess, but it doesn't work for
connectionStrings).  Other than that one, I can't access anything else
in the web.config file from the .dll at runtime.
--------------------
<configuration>
     <configSections>
       <sectionGroup name="applicationSettings"
type="System.Configuration.ApplicationSettingsGroup, System,
Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
         <section name="MyWebApp.My.MySettings"
type="System.Configuration.ClientSettingsSection, System,
Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
requirePermission="false" />
         <section name="MyDll.My.MySettings"
type="System.Configuration.ClientSettingsSection, System,
Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
requirePermission="false" />
       </sectionGroup>
   </configSections>
 <appSettings>
   <add key ="CAN_READ_THIS_FROM_BOTH_WEB_AND_DLL" value ="IT_WORKS"/

 </appSettings>

   <connectionStrings>
       <add name="aConnectionString" connectionString="Data
Source=localhost;Initial Catalog=&quot;C:\PROGRAM FILES\MICROSOFT SQL
SERVER\MSSQL.1\MSSQL\DATA\GENERIC.MDF&quot;;Integrated Security=True"
           providerName="System.Data.SqlClient" />
   </connectionStrings>

   <applicationSettings>
     <MyWebApp.My.MySettings>
           <setting name="ONLY_FROM_WEB_APP" serializeAs="String">
               <value>Can only access this from the web app</value>
           </setting>
       </MyWebApp.My.MySettings>
     <MyDll.My.MySettings>
       <setting name="WORTHLESS" serializeAs="String">
         <value>Can't access this value from anywhere</value>
       </setting>
     </MyDll.My.MySettings>
   </applicationSettings>

</configuration>