The title says it all...
+7
A:
Because the DLL contains metadata about all the types, methods etc. Even the actual code is in IL rather than native code.
Basically a .NET binary is still at a higher level than a native binary, and contains a lot more information about what's in there. That's what allows Reflection to work.
Jon Skeet
2009-10-02 05:28:31
So, is it accurate to say that C# gets compiled then? I'm asking because if I understand what you're saying, the IL then gets interpreted, right?
Esteban Araya
2009-10-02 05:38:13
If i understand it correctly, IL is JIT compiled to the proper machine code as necessary.
RCIX
2009-10-02 05:42:48
JIT = Just-In-Time compiler.
Robert Harvey
2009-10-02 05:43:26
Actually, both are true. On almost all .NET implementations, it is JIT compiled. But on "Micro Framework" it is interpreted. You aren't hugely likely to see Micro Framework much ;-p
Marc Gravell
2009-10-02 05:45:36
Mono also has a bytecode interpreter, and IIRC can be forced to use it via command line switches.
Pavel Minaev
2009-10-02 05:51:45
A "mixed" assembly can contain both managed and unmanaged code.
Dave Van den Eynde
2009-10-02 06:47:54
A:
It depends.
A DLL contains a list of functions exported, but these can be simply assigned a number, a name, or they can be assigned a mangled C++ name. The latter can give some insight in the function's parameters, but data structures, calling conventions and other required attributes are generally not documented.
If it's a COM DLL, there's a possibility that it contains a Type Library as a resource, but this is not guaranteed. In that case, .NET can import the library quite automatically.
A Type Library can also be included in a non-COM DLL, but this is not a widespread practice.
If you have a compiled DLL designed to be called from a non-COM, non-managed environment, you'll need to translate the header files that should be included with the DLL.
Dave Van den Eynde
2009-10-02 05:30:07
I believe the question is specific to .NET, so the C++/COM side - while interesting and accurate - doesn't really apply.
Marc Gravell
2009-10-02 05:41:41
This question is a response to my comment about another question regarding headers, so no, I don't think it's specific to .NET DLL's.
Dave Van den Eynde
2009-10-02 06:46:22
+1
A:
I'm not sure if that is what you are asking about, but I can only recommend the free tool .NET Reflector that lets you explore any compiled .NET assembly.
These days, I use it much more than I use even the published MSDN documentation, because it's much faster to navigate around in, and more informative to boot.
Mark Seemann
2009-10-02 05:31:44
I don't think it was apparent just what he was asking about, which was also why I qualified my answer by "I'm not sure if that is what you are asking about".
Mark Seemann
2009-10-02 07:39:18
Are you saying that Reflector will not provide exploration of metadata?
Abhijeet Patel
2009-10-02 16:59:02