http://ayende.comAyende @ RahienCopyright (C) Ayende Rahien 2004 - 2021 (c) 202660Specific experience is also an important topic - I've built OR/Ms twice. The first one took me about a week to get fully functional, and the second one - half a day; and they had the exact same features. That's because the second time I know *exactly* where the pitfalls would be, even though it was a year later. I didn't stop to think for a sec, I just coded on auto-pilot. which is probably what you do when you build an IoC container, or something like that. http://ayende.com/3713/building-frameworks-it-is-one-day-or-three-months#comment2http://ayende.com/3713/building-frameworks-it-is-one-day-or-three-months#comment2Sat, 22 Nov 2008 20:23:15 GMTA little bit OT. Some time ago in one of the ASP.NET MVC posts you've mentioned that you don't understand why there are so many sealed or non virtual classes in ASP.NET MVC. On last PDC Brad Abrams said that they've done that intentionally using the rule which can be expressed more or less this way: "open only those extension points which you have reasonable scenario to extend". (you can see a full PDC session at [http://channel9.msdn.com/pdc2008/PC58/](http://channel9.msdn.com/pdc2008/PC58/) ). Bad rule or bad use of rule ? Just curious your opinion... http://ayende.com/3713/building-frameworks-it-is-one-day-or-three-months#comment1http://ayende.com/3713/building-frameworks-it-is-one-day-or-three-months#comment1Fri, 21 Nov 2008 17:36:14 GMT