How to provide custom implementation for extern methods in .NET?

Question

In C# the extern modifier is used to declare a method that is implemented externally. Usually it is used with DllImport attribute to call some function in unmanaged code.

I wonder if there is a way to provide custom implementation of extern method?

To understand better the problem consider the following use case. I have a set of functions implemented in unmanaged code and I'd like to supply pointers to these function in run-time (during the loading of assembly).

The same thing DllImport attribute does, but I'd like to provide pointers by myself.

Answer 1

This is possible although you would need to PInvoke several things ( LoadLibrary and GetProcAddress - see links below)... it is called "late binding native code"...

Some relevant links with source:

• http://blogs.msdn.com/b/junfeng/archive/2004/07/14/181932.aspx
• http://www.codeproject.com/KB/cs/dyninvok.aspx
• http://pinvoke.net/default.aspx/kernel32/GetPRocAddress.html
• http://www.pinvoke.net/default.aspx/kernel32.loadlibrary

Answer 2

您将需要使用LoadLibrary和GetProcAddress