Hi I wish to use a C# library in a C++ application which is in unreal engine.
Is there any easy way to wrap a C# library using C++ ??
I have looked up how to wrap a C# library but there only seems to be posts on how to use a C++ library in C#.
Really appreciate the help thanks.
C# allows you to perform interoperability calls to c++ and c libraries. Although not exposed, you could manipulate your assembly to force the reverse (this is done via ildasm, however, this is a trick and I won't go in details).
To achieve what you ask, you have to manually fill in the gap from your c++ host and your c# library. One way, not clearly at zero effort, is to create a new assembly in MC++ (ie c++ with a hosted clr) . This bridging assembly would expose the api in order to be used by your c++ language, while it can access your c# library to reuse the logic.
This is not a trivial task as you need to manually marshal the data structures as you are going "against the designed use case".
Embedding a runtime, in my opinion, would have the same effort. In any case, you should be careful though, because your unreal engine is resource intensive and performances could get a sensible hit. Furthermore, the c# part has a different memory management system that can not be optimal when stressed by the unreal engine.
Related
I have worked extensively with C#, however, I am starting a project where our client wishes all code to be written in C++ rather than C#. This project will be a mix between managed (.NET 4.0) and native C++. Being that I have always preferred C# to C++ for my .NET needs, I am wondering if there are any important differences I may not be aware of between using C# and managed C++?
Any insight into this is greatly appreciated.
EDIT Looking at Wikipedia for managed C++ code shows that the new specification is C++/CLI, and that "managed C++" is deprecated. Updated the title to reflect this.
C++/CLI is a full fledged .NET language, and just like other .NET languages it works very well in a managed context. Just as working with native calls in C# can be a pain interleaving native C++ and Managed C++ can lead to some issues. With that said, if you are working with a lot native C++ code I would prefer to use C++/CLI over C#. There are quite a few gotchas most of which could be covered by do not write C++/CLI as if your were writing C# nor write it as if you were writing native C++. It is its own thing.
I have worked on several C++/CLI projects and the approach I would take really depends on the exposure of different levels of the application to native C++ code. If the majority of core of the application is native and the integration point between the native and managed code is a little fuzzy then I would use C++/CLI throughout. The benefit of the control in the C++/CLI will outweigh its problems. If you do have clear interaction points that could be adapted or abstracted then I would strongly suggest the creation of a C++/CLI bridging layer with C# above and C++ below. The main reason for this is that tools for C# are just more mature and more ubiquitous than the corresponding tools for C++/CLI. With that said, the project I have been working on has been successful and was not the nightmare the other pointed to.
I would also make sure you understand why the client is headed in this direction. If the idea is that they have a bunch of C++ developers and they want to make it simpler for them to move to write managed code I would posit to the client that learning C# may be less challenging then learning C++/CLI.
If the client believes that C++/CLI is faster that is just incorrect as they all compile down to IL. However, if the client has a lot of existing or ongoing native C++ development then the current path may in fact be best.
I've done a project with C++/CLI and I have to say it was an abomination. Basically it was a WinForms application to manage employees, hockey games, trades between teams, calendars etc, etc...
So you can imagine the number of managed controls I had on my forms: calendars / date time pickers, combo boxes, grids etc.
The worst part was to use only C++ types for my back-end, and use the managed types for the front-end. First off you can't assign a std string to a managed string. You'll need to convert everything. Obviously you'll have to convert it back...
Every time I needed to fill a grid, I serialized my C++ collections to something like a vector<std::string>, retrieve that in my UI library and then looped trough that and made new DataGridRow to add them to the grid. Which obviously can be done in 3 minutes with C# and some Linq to SQL.
I ended up with A+ for that application but lets be honest it absolutely sucked. I just can't imagine how pathetic the others app were for me to get that.
I think it would've been easier if i used List<Customer>^ (managed List of some object) in my C++ instead of always converting everything between vectors of strings. But I needed to keep the C++ clean of managed stuff.
/pissedof
From using all three areas (.NET, C++/CLI and C++) I can say that in everyway I prefer using .NET (through C# or VB.NET). For applications you can use either WinForms or WPF (the latter of which I find far better - especially for applications that look far more user friendly).
A major issue with C++/CLI is that you don't have all the nice language features that you get in .NET. For example, the yield keyword in C# and the use of lambda (I don't think that's supported in C++/CLI - don't hold me to that).
There is, however, one big advantage of C++/CLI. That is that you can create a bridge to allow C# and C++ to communicate. I am currently working on a project whereby a lot of math calculations and algorithms have already been written (over many years) in C++, but the company is wanting to move to a .NET-based user interface. After researching into various solutions, I came to the conclusion that C++/CLI was far better for this. One benefit is that it allowed me to build an API that, for a .NET developer, looked and worked just like a .NET type.
For developing an application's front end, however, I would really not recommend C++/CLI. From a usability point of view (in terms of developer time when using it) it just isn't worth it. One big issue is that VS2010 dropped support for IntelliSense for C++/CLI in order to "improve general IntelliSense" (I think specifically for C++). If you haven't already tried it, I would definitely advise checking out WPF for applications.
Currently, we are working on a C++ legacy code base, which consists of several software components.
One of the components, are written in a way that is extremely difficult to maintain. (For example, memory allocation is done in X place, but memory de-allocation is done in Y place. This make memory management a painful job). Till now, we able to solve (or workaround) all the memory leakage issues.
However, after several rounds of bug fixing, our feeling is that, due to the high maintenance cost of this software component, we are unable to go too far from current milestone.
I know it might be bad to rewrite the source code : http://www.joelonsoftware.com/articles/fog0000000069.html
However, instead of re-factor the current code, we forsee it will be better to re-write from scratch due to
Till now, no one in the team can fully understand that software component code.
The legacy software component is a small piece of software. 20k lines, I guess
Our teams are pretty clear on the requirement and what we are trying to achieve
Hence, we are planning to go for a managed code, at least make memory management a painless job. We plan to choose C#, as
All our C++ code are compiled using Microsoft VC++
We are using MFC, in other software components. (in DLL form) Every DLL, do have their very own resource.
I am from C++ and Java background, and know nothing much on C#.
How well C# to interface with MFC DLL, with some of the DLL functions will invoke MFC GUI?
Anything I need to pay attention on it?
Will the interfacing with legacy C++ DLLs be easier, if we are using Managed C++?
Thanks.
I am in a similar situation and I also did some experiments mixing C++ and C#. The problems in my application however were that:
the application is not clearly split up in different modules, making it hard to move specific modules from C++ to C#
the application is quite cpu-intensive and experiments revealed a big overhead in calls from C++ to C# or C# to C++
Additionally, you cannot call C# directly from native/unmanaged C++, which meant that I had to introduce an additional intermediate C++/CLI (or is this called C++.Net?) layer.
Therefore, I chose not to move to C#, but stay with C++.
So, if you want to move from C++ to C#, make sure:
that you have clearly separated modules
that the transition (calls) from C++ to C# or vice versa are in a place that is not used that often (so not during cpu-intensive tasks)
Additionally, remember that if you are not the sole developer of the project, that all (or most) of your developers should also learn C#. You don't want to delegate all C# code to your latest junior developer, because if he leaves, you will be (or could be) in trouble.
How well C# to interface with MFC DLL, with some of the DLL functions will invoke MFC GUI?
Not well at all. You can't P/Invoke to a C++ library -- it works with C exports only. You would need to write a wrapper exposing a C library interface for you to P/Invoke from C#, or you'd need to recompile MFC using C++/CLI. There's little reason to do this though as Winforms is a comparable library to MFC for .NET code.
Anything I need to pay attention on it?
I don't understand that question.
Will the interfacing with legacy C++ DLLs be easier, if we are using Managed C++?
Considering you can't do it using C#, yes. You'd have to recompile those C++ DLLs to have them expose a C interface, or you'd have to recompile them from source using C++/CLI.
Note: No matter what you do here, you're still going to have to worry about memory managment and object lifetime of anything going on inside native code. The CLI does not automatically manage native resources for you.
If you had to decide between C# and Managed C++, which would you choose and why?
Are there benefits of Managed C++ over C#? Which language do you prefer? What decisions would you make under what circumstances?
I would use managed C++ if I:
Needed to integrate with existing C/C++ code
Needed to port existing C/C++ code to .net
Needed to use .NET objects from C++
Needed to expose .NET object over COM in a more complex way than what .net makes easy
Needed to access hardware directly
Needed to call lots of unmanaged APIs
And already had some skills in C++, as the above tasks will need a experienced C++ programmer. Most of the time I would only consider managed C++ if the company already had a C++ code base, otherwise who is going to maintain the managed C++ code.
In other cases I would always choose C#. Even if I choose managed C++ for part of the system, I would try to write as much of the system as possible in C#.
Think of manage C++ as a bridge building kit for going between the
unmanaged world of C/C++ and the
managed world of .NET.
If you only need to call a few simple APIs from C#, then see pinvoke.net and this overview to find how to call them from C#, as a few lines of complex pinvoke code (prebuilt bridge) in C# is normally better then introducing C++ to a project that is not already using it.
what is the benefit of managed C++
over C#?
C++.net is useful for interacting with C++ and C code (that is, calling external C or C++ libraries, providing callback functions to external modules written in C or C++ and so on.
what language of both would you
prefer?
I would prefer C# for all situations except the one described above (interacting with C and C++).
C# is easier to write, simpler, and geared specifically to use the .NET platform. C++ can do it also, but it has all the complexity of the C++ language plus the extensions needed to use the .NET platform.
Unless you need to interact with native C++ or C code, you're better off using C# in most cases (that is, if you're coding for the .NET platform).
Normally I prefer C++, but when needing to code for .NET, it doesn't beat C#.
Managed C++ is good for interop with C++: for example, if you have a .NET application and your assembly has to interact with a native interface that comes as C++ .lib files (which I had more than once), or with a nice C++ API.
Example: Rithmic (not that you ever heard of them) until recently ONLY supported a C++ API. If you try to access them from C# - good luck ;) Managed C++ allows me to access their API and expose nice .NET objects.
Basically interop. Managed C++ REALLY shines in interop with low level C / C++ API's.
I used managed C++ when I needed to build up new NET component with much ofC++ unmanaged code inside.
I did a specific class used to Marshall some objects forward and back from old C++ code.
I've encountered a problem which was transparent in managed C++, but made a big headache in C# - I had to send a callback function to a C++ unmanaged library, that defined this callback as __cdecl. In C#, the default calling convention is __stdcall, and it is pretty compilcated to move a C# delegate from __stdcall to __cdecl (Actually it requires either a 'shim' unmanaged DLL to do so or using some reflection classes).
In C++, (C++.Net as well), it is just a simple attribute.
I haven't personally written, or read for that matter, too many lines of code in managed C++, but from what I have seen it looks too convoluted and patchy. That said, you might want to use managed C++ if you are really good in C++, and when learning the idioms and patterns of a new language would be too much of a risk.
Use C# if you are quite competent in it. If you are only getting started with C++ and C#, I think, C# is the easier route to take.
I would prefer C#, or specifically .NET, over C++ because of the extensive .NET standard library.
I have a native C++ DLL using DirectX, that I want to be able to use through C# to be able to create content creation tools.
Adding COM would require quite an effort it seems.
Can P/Invoke be used to maintain classes using polymorphism, or would it require me to wrap most of the code to facilitate use of P/Invoke?
It there a better solution is available? Or should I even consider writing the tools in C++ using Qt perhaps?
I always feel that C++/CLI is always the best option when doing C# to C++ interop. You can easily create thin wrappers for an unmanaged library that will look exactly like a managed library to your C# code. It also gives you more control over how marshaling and pinning is performed.
There are ways to automatically generate C++/CLI I believe, but I've never used them.
More info on C++/CLI here:
http://msdn.microsoft.com/en-us/magazine/cc163681.aspx
I presume rendering with D3D directly from C# isn't an option? (because that certainly would be easier!)
A long time ago, I used SWIG to automatically maintain C# "bindings" of my C++ rendering DLL code. It uses P/Invoke to expose the C++ objects on the C# side, and you won't have to maintain that code anymore.
You don't need to write wrap on QT.
I advice you to write Observer class both in C# & C++, and hide calls of Native functions to it.
Schema is like this
Your code in C# -> Observer(C#) -> Native call to Observer(C++) -> Calls to your dll.
I'm currently in a project that need to work both on Mac and Windows. We are using standard portable C++ for all the application logic. However, since we want the app to feel totally native on both platform, the GUI will be written with C#/WPF for Windows and Objective-C/Cocoa for Mac.
However, for the windows part, I am wondering what is the best way to use the C++ code with C#. C# is managed, and I know that we can use managed C++ too. However I worry that using C++ inside the CLR may introduce unexpected bugs, or that we will need to put an awful lot of #ifdef WIN32 everywhere in the C++ code to make it work both with the managed CLR and the unmanaged environnement of Mac OS X (note that we sure expect to put some ifdef, but we'd like to keep it under control if possible). So basically, what is the best way to use the C++ code with the C# code? Right now, I'm thinking of three solutions
1- Compile the C++ as C++/CLI and directly use the classes and function from C#.
2- Compile and wrap the C++ in an unmanaged win32 dll and call it from C# using DllImport
3- Wrap the C++ in a COM wrapper and use the .NET COM Interop to link it with C#
Which one is the best way? Or, if there is a better solution, what is it?
C++/CLI has several restrictions over standard C++ that don't always make it easy to recompile standard C++ as C++/CLI. Keep in mind that you'll have to distinguish 'managed' and 'unmanaged' pointers, for starters. As these are using different symbols, you've got your first set of #ifdefs right there. And then you get to ref and value classes and all that sort of fun.
You can however use C++/CLI to bridge the gap between native code and the .NET world. The last time I did something along the lines of what you're planning to do, I used C++/CLI to write the bridging layer that did the necessary translation and conversion work between .NET types and classes and the native world. The C++/CLI layer can obviously be used from any .NET language.
You can't always use (2) - this depends very much on the data types you're trying to exchange between the two worlds. The .NET marshalling code is pretty good at dealing with C PODs but anything more complicated and you've got a problem.
(3) is overkill IMHO and introduces another point of failure, plus you're then doing .NET <-> COM <-> native instead of the simpler .NET <-> native if you created your own bridging code. Not to mention that you add complication to your code that won't benefit the other OS you're targeting, namely OS X.
Our development team has been using C++/CLI compiled code with ASP.NET and WPF front ends for while now.
The first major issue we had was build time. The code base would be 150k lines (40+ projects) and took forever to link (due to linker issues we could not build the individual projects as DLL's). We were only able to resolve this issue by wrapping the code with managed C++ classes and building our projects as assemblies.
The second major issue was performance. We originally compiled with /clr (before pure option existed) and this resulted in double thunking of most of our calls that occurred in the managed C++ layer. We fixed this by switching to /clr:pure. By doing so we ran into an
issue where our assemblies resulted in having too many 'global' methods in the assemblies so they would not load. We had to split our assemblies further to solve this issue.
Best and easier way is to do it with .NET <-> COM because COM has much stronger bridge compared to native dll access inside .NET because it may lead to lots of memory issues and lots of troubleshooting time. Its easier to test COM inside any MFC project and get the trace information for debugging and when the component is ready it can be easily used inside .NET.
CLI will not let you use all features and unfortunately its fairly new so less documentation is available and you will not get good support for your questions.
Win32 dll and DLLImport has problems mainly to troubleshoot, because the exception thrown inside Win32 dll will not travel further along the stack instead it will simply crash and you will not get the reason. Where else in COM you can catch exception internally and the COMException thrown inside .NET will not crash your entire application.
COM will be little slower in performance, but it will be more organized and good design pattern to develop.