Today, I worked with services logic that sends me light objects mapped from NHibernate entities with AutoMapper, and I got an exception stating that something is wrong with mappings. I wrote UT that reproduces my issue and surrounded code with try{}catch(){} to see exception closer, and it said me the same I saw. I took a look on Inner exception message and at first glance it was absolutely identical to parent message.

Then I spent about 10-20 minutes verifying all my entities, trying to find some stupid mistake and I would spend more if I would not take a look on Inner exception of the Inner exception and it was a bit different, saying that another entity mapping is wrong, so I took a look into Inner exception of it and so on…

So do you have an idea where did I stop? See:

So I went through 11 Inner Exceptions to get to the null Inner Exception :) Highlighted message provided me information I needed to resolve my issue.

Moral: Always take a look into Inner Exception!