How to use existing C++ code in .NET (C#)

Question

Hi,

I would like to create a C# project and implement the existing native (C++) code. Does anyone know about any good tutorial about it?

Thanks!

Answer 1

You can use P/Invoke and you can call unmanaged methods. I'll post you some examples: This is a reference to MSDN official documentation. This is a community mantained website with most of the common Windows unmanaged libraries along with method signatures and examples

Answer 2

Why don't you try managed wrappers for your C++ code.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vcmxspec/html/vcmg_accessingcodefromframeworkobjects.asp

Answer 3

If your C++ code is managed (as you say), then I'd suggest that you leave it as C++ unless you have a very good reason to -- future C# (etc.) assemblies should be able to just reference it 'as is'.

Answer 4

Probably the easiest way to do this is to create a C++/CLI project, which will enable you to mix managed and unmanaged C++. You can then wrap your existing unmanaged C++ classes with a managed .Net wrapper that your C# code can call directly. MSDN magazine has a good introductory article on C++/CLI.

Interop will only really be useful for calling C-style functions. You can't really use it to interact with pure C++ classes.

Answer 5

I learned this by doing it, so I don't have a good tutorial, but there are a couple things you need to be aware of - managed C++ and C++/CLI both integrate with unmanaged code with very few ugly seams. This is not the case with C#. In managed C++, it's quite possible to do something like this:

dotNetForm->Text = S"My Project"; // regular managed code
::SetWindowText(dotNetForm->Handle, "Your Project"); // mixed managed/unmanaged

whereas in C# you would have to P/Invoke into SetWindowText--not that you really would: it's just a simple example, but you need to be aware that the managed C++ compiler is a weird combination of doing a lot of interop for you transparently and doing nothing for you at the same time (ie, it will do no implicit marashalling).

Answer 6

I assume by implement the existing code you mean you want to call it from C#, with minimal changes to the C++ code.

I'm a fan and recent purchaser of the book C++/CLI in Action which has a couple of useful sample chapters online.

This intro on CodeProject is a good starting point.

The author of C++/CLI in Action has a number of articles on CodeProject, scroll down to the C++/CLI section on his index.

The Wikipedia article on P/Invoke has a number of reasons why you might not want to use that approach, with which I agree:

• loss of typing support by the compiler
• possible data type or alignment issues as you have to map types by hand
• need to pin garbage-collected objects

The best starting point on MSDN is the summary article.