Porting C++ to C#

Question

C++ and C# are quite simmilar programming languages, in my opinion. If a C++ code needs to be ported to platform where C# is the only supported platform, how much work will need to be done?

Should I get ready, that most of the C++ code will need to be rewritten to C#? Or, because of language simmilarities, should refactoring be quite easy and straightforward?

I am aware, that it will depend on the application itself, but I am asking in general.

Answer 1

I have done a major port of a C++ application to C# recently. Overall I thought it was a pleasant experience. These are the steps that I took, they might or might not apply to your application.

1. Get the "scaffolding" in place in C#, design your architecture. This is the time to get in major architecture changes from the existing application if you choose to do so.
2. Get your tests in place. I can't over-emphasize this one. Since you are porting an existing application you should have a set of tests already in place that verify the correct behavior of your application. You can and should reuse these tests for your C# application. This is the one thing that gives you an edge when porting - you know (and have written) already many of the tests you want. Start porting your test project.
3. Put in method stubs for your C# methods that reflect the existing C++ methods. Given the framework support in C# some methods might not be needed at all anymore, or are very simplified - this is the time to decide.
4. Copy and paste. Yes I used copy and paste for most of the C++ code - all the flow statements basically can be reused if you are careful. Once pasted go through line by line, many things like use of pointers etc. must be rewritten to use a equivalent C# type.
5. Once you have re-written a method in such a way, do the obvious re-factoring given the framework support / helper classes you might have been lacking in C++ but are readily available in C#. Also naming conventions for variables etc. can be changed here, should be straightforward given the built in support for this in VS 2010.
6. Run your tests! Test early and often that the overall framework you have in place so far produces the exact same output as your C++ application which you can use as a reference. This is also the time to add missing tests.
7. Refactor, Refactor, Refactor. Every application ages, and so did your C++ application most likely. Look closely at the underlying design and simplify and remove as much as possible. Verify at each step by running your tests.