title: Is it possible to initialize a ConfigurationSection from an external file?
body: <p>I have a custom configuration property in my app.  It looks something like this:</p>
  
  <pre><code>public class OverrideConfiguration : ConfigurationSection
  {
      [ConfigurationProperty(PROP_ADMIN_CONNSTR)]
      public StringConfigurationElement AdminConnectionString
      {
          get { return base[PROP_ADMIN_CONNSTR] as StringConfigurationElement; }
          set { base[PROP_ADMIN_CONNSTR] = value; }
      }
  
      // .. Various other properties, but you get the idea
  }
  </code></pre>
  
  <p>However, what I'd like is to allow the .config file to be pointed to an external file source.  Something like this:</p>
  
  <pre><code>&lt;ServiceOverrides file="Overrides.local.config" /&gt;
  </code></pre>
  
  <p>Now, the built-in <code>configSource</code> attribute is <em>close</em> to what I need, but it has two major issues.</p>
  
  <ol>
  <li>Files <em>must</em> exist.  If the file doesn't exist, it errors out.</li>
  <li>Files must be in the current directory or in a <em>deeper</em> directory.  In other words, I can't point to <code>..\Overrides.local.config</code></li>
  </ol>
  
  <p>What I want is pretty much identical to the <code>&lt;appSettings file="..." /&gt;</code> configuration element.  However, that attribute seems to be something <code>appSettings</code> implemented, and is not part of the base <code>ConfigurationSection</code> class.</p>
  
  <p><strong>My Question:</strong></p>
  
  <p>Is it possible to override something in <code>ConfigurationSection</code> that will basically read XML data from a different location?  I don't want to change any other aspect of my class or do my own XML deserialization or anything.  I simply want to check if a file exists, if so, load in the XML contents from <em>that</em> file, otherwise load in the default XML contents.</p>