Recently I been involved in building variety of Biztalk pipeline components with different design-time properties ranging from simple "string" to "complex collections". I struggled a bit to figure out the ways to do it, due to poor error description you get while developing and also due to lack of documentation around it. Normally you'll find some blog articles here and there explaining stuff, but in this particular instance I couldn't find any blog articles either. So, I went ahead and written a white paper explaining design-time properties in Custom Pipeline component, the article explains using complex types and their serialization techniques, development tips and error diagnosis procedures.
You can download the White Paper and the accompanying code from the following location:
http://www.microsoft.com/downloads/details.aspx?FamilyId=8C2572A2-FB61-4016-A7A7-1C37518B39FF&displaylang=en
I need to thank Angus Foreman (from Microsoft,UK) and Luke Nyswonger for their help in publishing the article. I also would like to thank all the editors.
Nandri!
Saravana