How do exceptions work (behind the scenes) in C#

Question

Identical to "How do exceptions work (behind the scenes) in C++", but for C#.

I know that the steps below have to be performed when an exception is thrown.

1. Find the nearest handler for the exception type;
2. Unwind the stack up to the handler level;
3. Call the handler;
4. Find and call every finally blocks.

How does .NET handles these operations? How does the mapping for the "current" handlers work? How much code is emitted in a try/catch block? And in a throw block?

Answer 1

.NET exceptions on Windows use the OS' underlying Structured Exception Handling (SEH) mechanism, in the same way as native code. As listed in the linked question for C (and C++).

Answer 2

.NET exceptions use the underlying Windows structured exception handling implementation, though this is not a requirement. Mono may do it differently.

In fact, if you write a single-line Console app that just throws an exception, and then run it in Windbg, you'll see the hook into the unmanaged exception handling.

Answer 3

Read Christopher Brumme's article; it gives a very detailed explanation of what happens behind the scenes in CLR exception handling:

http://blogs.msdn.com/b/cbrumme/archive/2003/10/01/51524.aspx