Adding unknown (at design time) properties to an ExpandoObject

Question

just exploring c# 4. Trying to get my head around all this dynamic stuff. Sorry if this question is silly, no experience in this domain.

If I have an ExpandoObject a

Answer 1

The answers so far cover the basics quite well, but I felt this MSDN Magazine article was worth sharing as well:

http://msdn.microsoft.com/en-us/magazine/ff796227.aspx

It covers some examples of using dynamic XML input to dynamically create and use ExpandoObjects.