Ayende @ Rahien

My name is Oren Eini
Founder of Hibernating Rhinos LTD and RavenDB.
You can reach me by phone or email:


+972 52-548-6969

, @ Q c

Posts: 6,124 | Comments: 45,470

filter by tags archive

Brail UpdateFixing AmbigiousMatchException for lazy loaded classes

time to read 3 min | 418 words

There is probably a bug in Dynamic Proxy that causes it to output overrides to methods in such a way that when you reflect over the generated types, you get two methods for each overriden methods, instead of a single overriden method. I looked into it in detail a while ago, and I couldn't figure out how to make it work like I expect it to. The code that it generate is verifable, so this is something that the CLR supports, but I am not quite sure that I understand what the semantics for this is.

So, what does this have to do with Brail? NHibernate makes extensive use of DynamicProxy in order to increase performance and to defer loading, which meant that any application using NHibernate had this issue. Now, Brail is a dynamically typed langauge (well, not really, but that is close enough), which means that it uses Reflection to resolve properties and methods that are called. Because of Dynamic Proxy generated what is basicaly a duplicate method, that failed.

At the basic level, it meant that a call like this:


Would turn into:

blog.GetType().GetProperty("Name").GetValue(blog, null);

(This is actually very far from how it is wokring but again, that is close enough to make sure you understand the problem.) Now, GetProperty("Name") woudl throw an AmbigiousMatchException, since it actually found two properties called "Name", one of the original class, and the second on the proxied class.

Why am I boring you with this? The fix for this was fairly simple, but it involved simply replacing the way Boo (which is what Brail is using) type system with my own. The fast that I could do that with roughly 350 LoC is quite amazing to me.  This also means that I can actually preserve the dynamic nature of Brail, but behind the scene generate strongly typed accessors (think Dynamic Methods), which would elevate any concerns about reflection costs.

The code is in the Castle's trunk now, so you can start using it.

More posts in "Brail Update" series:

  1. (25 Feb 2007) Fixing AmbigiousMatchException for lazy loaded classes
  2. (24 Feb 2006) Nullable Parameters


Pierre Henri

Impressive how you explained every single detail ;)

Ayende Rahien

I can't figure out if that was a good or a bad thing...

Comment preview

Comments have been closed on this topic.


  1. RavenDB 3.5 whirl wind tour: You want all the data, you can’t handle all the data - about one day from now
  2. The design of RavenDB 4.0: Making Lucene reliable - 3 days from now
  3. RavenDB 3.5 whirl wind tour: I’ll find who is taking my I/O bandwidth and they SHALL pay - 4 days from now
  4. The design of RavenDB 4.0: Physically segregating collections - 5 days from now
  5. RavenDB 3.5 Whirlwind tour: I need to be free to explore my data - 6 days from now

And 14 more posts are pending...

There are posts all the way to May 30, 2016


  1. RavenDB 3.5 whirl wind tour (14):
    29 Apr 2016 - A large cluster goes into a bar and order N^2 drinks
  2. The design of RavenDB 4.0 (13):
    28 Apr 2016 - The implications of the blittable format
  3. Tasks for the new comer (2):
    15 Apr 2016 - Quartz.NET with RavenDB
  4. Code through the looking glass (5):
    18 Mar 2016 - And a linear search to rule them
  5. Find the bug (8):
    29 Feb 2016 - When you can't rely on your own identity
View all series



Main feed Feed Stats
Comments feed   Comments Feed Stats