<p>I started using <a href="http://www.codeplex.com/SHFB" rel="noreferrer">Sandcastle</a> some time ago to generate a Documentation Website for one of our projects. It's working quite well but we've always only written documentation for classes, methods, properties (...) in our project and had completely separate documentation for the overall project and project parts/modules/namespaces. It would be nice if I could merge that documentation together and add respective documentation to the generated helper files but I can't figure out how to do it.</p>

<p>Just adding comments to the namespace declaration doesn't seem to work (C#):</p>

<pre><code>/// &lt;summary&gt;
/// My short namespace description
/// &lt;/summary&gt;
namespace MyNamespace { ... }
</code></pre>

<p>Does anyone know how to do this? I know it's possible somehow and it would be really nice to have... :)</p>

If you use
Sandcastle Help File Builder
there is a dialog to enter the Namespace summaries. (Apparently also support for defining a specific class, but I wouldn't prefer it..)
From the feature list:
Definition of project summary and
  namespace summary comments that will
  appear in the help file. You can also
  easily indicate which namespaces to
  include or exclude from the help file.
  Support is also included for
  specifying namespace comments via a
  NamespaceDoc class within each
  namespace.