Managed C++ wrappers for legacy C++ libraries

Question

We\'re looking at writing a .Net-callable wrapper for some legacy C++ libraries using managed C++.

It all looks pretty easy. Is there anything we need to watch out

Answer 1

It is pretty straight-forward and works well. It is a lot easier than PInvoke.

The big thing you need to watch out for is not having any unmanaged members in your managed headers, including private members, method signatures, etc. It is okay to have private members that are pointers to managed types though, just use forward declarations for your classes.

Also, watch out for object lifetime. It is easy to introduce memory leaks since many .NET programmers are not used to cleaning up after themselves. Make sure any wrapper classes that you create are disposable if they contain pointers and make sure you dispose of them in your managed code. The syntax for IDisposable in managed C++ is also weird, but it is in the docs.

Also, remember that you incur a slight hit every time you cross the managed/unmanaged boundary, so try to plan your interface accordingly. If anything gets called repeatedly in loops, it is probably better to move that loop across the boundary so you only cross once. Don't worry too much about this though unless you are talking millions of calls.

This article goes the other way, but it has some useful points.

Use Our ManWrap Library to Get the Best of .NET in Native C++ Code

See also

Managed Code in Visual Studio 2005 and
Deleting Managed Objects, Wrapping a Library, and More