title: Attaching properties and methods at runtime in C# 4.0?
body: <p>What are the performance implications of attaching methods and properties at run time using dynamic features, as described in <a href="http://amazedsaint.blogspot.com/2009/09/systemdynamicexpandoobject-similar.html" rel="noreferrer">this blog post</a>? </p>
  
  <p>What are the practical uses of ExpandoObject?</p>