Good day,
I want to take an existing C# project and wrap functions into a C++/CLI DLL. I need to be able to read this DLL from VB 6. I choose this route because I won't have to register a .net DLL in order to use it with VB 6. Frankly I have no experience with this kind of thing so I would greatly appreciate a good example. I know there are plenty of similar questions like this but I haven't been able to find anything simple enough for me to understand.
This is a fairly unwise route to pursue, making C# code [ComVisible] is pretty trivial and Regasm.exe should not scare you. The usual mistake with Regasm is to forget to use its /codebase option on your dev machine.
If you insist on not taking advantage of this then you'll need to find a way to get the CLR loaded yourself so it can execute your C++/CLI and C# code. There are three basic ways to do so. You've written off COM interop and hosting the CLR yourself isn't very practical if the host app is VB6. You however can take advantage of the C++/CLI compiler's ability to generate unmanaged DLL entrypoint stubs that load the CLR for you and switches to managed code execution. Do so by writing a static function that you decorate with __declspec(dllexport). The technique is shown in this answer. Beware that it isn't particularly performant and you'll have to live with the restrictions imposed by the VB6 Declare statement.
Also check this post-processing tool that can inject these stubs directly into a C# assembly. Not sure how reliable it is, I haven't used it myself.
Be a man and make that DLL under a couple of different compilation/linking/function-call-protocol configurations. Then go ahead and try a couple of different referencing configurations in your VB6 project. Post what works. Contribute, go forth!
Take a look at Export Managed Code as Unmanaged
and C# Project Template for Unmanaged Exports
Related
I have C++ Qt application together with a lot of .net C# assemblies, that I would need to use in the C++. Before doing any research I was expecting there is existing solution to generate C++/CLI wrapper DLL for usage in pure C++ app, but to my surprise I wasn't able to find anything except SharpCpp, but that's just experiment.
As the amount of classes that need to be exposed might be pretty extensive, I was looking for as much as automatic solution possible ( like what I'm used to when wrapping C++ for Python using shiboken)
As far as I can tell my possibilities are (as just compiling the app with /clr is not an option):
Manually write C++/CLI bridge DLLs, but this could take a lot of time.
use COM, but that would also mean a need to implement the COM exposure to all C# assemblies also. Or is there any automated solution?
use CLR Hosting. Not an option without automatic generation of the wrapper also.
try using something like Alter-Native or cs2cpp, but I don't know how much production ready this is.
So I was wondering, if someone was facing similar problem, and what turned out to be the best, and most maintainable solution.
Attempting to build a C# NPAPI plugin I have found a tutorial which describes that your dll needs to implement a number of methods such as NP_GetEntryPoints , NP_Initialize and NPP_New along with a number of others.
However what I want to understand is if I can simply mirror these method names and construct equivalent datastructures as described in the article (like _NPPluginFuncs) in C# and everything will work?
Could someone please be kind enough to provide some guidance? Is it possible to build a NPAPI plugin in C# and if so what are the basic steps involved?
As stated in the documentation:
A NPAPI browser plugin is, at it’s core, simply a DLL with a few specific entry points
That means you need to export some function from a regular dll, that is done usually in C/C++. Unfortunately it is not possible to expose any entry point from a plain C# dll, but look at this answer, with some effort it appear to be possible to trick some export by some sort of post build tool.
In any case don't expect to pass too much complicated data structures from/to the plugin interfaces, it will be a pain. If you are interested in doing more research the keywork to use is "reverse P/Invoke", in analogy with direct P/Invoke that is calling regular dll from managed world.
The reason a C# dll can't expose directly "entry points" is that entry point are actually just some address inside the dll poiting to some assembly code immediately executable. C# dll are different kind of beast: they are just files containing IL that is compiled "Just In Time" and indeed such compilation is forced AFAIK with some OS tricks. This is the reason reverse P/Invoke is not starightforward at all.
As Georg Fritzsche says in his comment:
NPAPI plugins are basically DLLs with a few required C-exports
and there is no built-in way to export functions (in the C-export sense) from an assembly written in C#.
Some of your options are:
A mixed-mode C++ assembly which can export the functions directly. This could have implications for hosting the CLR in your plugin's host process.
A small native DLL which hosts the exports, then uses COM interop to delegate to a C# assembly containing the plugin functionality. The "official" way to do so-called "reverse p/invoke".
An intriguing project which post-processes your fully-managed assembly, turning static methods marked with a custom attribute into named function exports. (I have no affiliation with this project; I stumbled across it after I got to wondering whether anyone had improved on the COM interop way of doing things.)
I´m really in the need of getting a deeper understanding of how to set up things right to get an elegant interaction between my C++ and C# code bases.
What I want to achieve is an in-game editor written in C# for my game engine (C++/DX). For doing so I let VS build my engine as a C++ dll with some additional functions (unmanaged code) to access the required functionality of my engine from the C# editor code base. So far so good.
The first thing which is bugging me is that I´ve to build the dll with CLR support. Otherwise C# does not accept the dll for some reason. It doesn´t even allow me to add it to the resources ("A reference to 'C:\Users...\frame_work\Test\frame_workd.dll' could not be added. Please make sure that the file is accessible, and that it is a valid assembly or COM component.").
And when I build the dll with CLR support and add it to the references in C# ,re-build without CLR support, start my editor and make a function call from the dll then I get an Exception HRESULT: 0x8007007E. I searched for it but the only thing I found had to do with dependencies but that doesn´t fit to the alert I get when adding the dll to the resources.
The other point is that I always have to switch the configuration type between application (.exe) and dll. in VS C++ depending on whether I want to run my engine directly or from the editor and every time the complete project is build completely new.
So, could someone explain to me how to organize this the right way? And what could be a possible reason why C# wants the dll to be compiled with CLR support?
Thank you guys/girls.
There are two ways to deal with this.
Either you make your C++ code provide an API which has a fully compliant COM object. If the object is COM then C# can directly interop with it. (This is why you can't add it as a reference directly)
However I think what you are really wanting to do will involve a P/Invoke (calling C/C++ native code from C#). This is entirely possible but it's not always easy. You need to deal with conversions between your C++ API and your C#, pointers and you need to be very careful to pin any references that your C++ code writes to in the C# app.
C# code is managed code (runs in the CLR), and can only directly* reference managed assemblies. So of course you're getting an error when you build against a managed assembly, and then sneak in and replace that managed DLL with an (incompatible) unmanaged DLL. You're basically trying to lie to the compiler, and that generally doesn't end well.
If you want your C++ DLL to be accessible from C#, the simplest way to do it is to build it as a managed assembly (i.e., CLR support). Which you're already doing. Just take out the extra step where you replace the working managed DLL with a non-working unmanaged one.
Also:
C++ dll with some additional functions (unmanaged code) to access the required functionality of my engine from the C# editor
That won't help you, because C# can't directly* call unmanaged code. The simplest way to make this work will be to make additional managed classes and methods in your C++ DLL. Then your C# assembly will be able to directly use those managed classes.
* As Spence noted, you can use -indirect- means (P/Invoke and COM) to access unmanaged code from C#. But that will make your life much more complicated than it is now, not to mention how it will complicate your build and deployment. You're already really close to something that should work -- don't add all that extra complexity.
When calling functions with P/Invoke, you don't add the DLL to the C# project resources (or what you probably meant, references, either).
You will add it to the file list in your MSI project, of course.
We have native Win32 C++ code and a set of C# assemblies which we wish to call from the C++ code. I summaries our optios as:
Use COM. The C# code would need to be decorated with additional attributes (GUID, COMVisible). The C# assemblies would need to be registered regasm and would then be available to the native C++ code via COM.
Use a C++/CLI (formerly managed C++) wrapper class. A C++ class could be added to the native C++ project. That class would be compiled with /clr. The native C++ code would call the C++/CLI class which would then call the .Net code. No COM involved. The CLR is started by magic as required with marshalling handled by the C++/CLI extenstions.
Host an instance of the CLR in the native C++ code.
I'm going to discount option 3 as I don't see the benefits over option 2 other than we lose the need for a wrapper class. So the question is, what are the pros/cons of option 1 versus option 2?
Thanks in advance.
Option 2 will perform the best, and be the most seamless and maintainable, IMO.
There is really no advantage to option 1 that I've found. Using C++/CLI seems to function much better, work faster, and be much simpler in general.
You also can, btw, just use the C# assembly directly without having a wrapper class. This does require compiling any files that want to use it with /CLR, but it works quite well.
For option 1 your main pro would be not having to write a wrapper class which can get hairy depending on your project.
For option 2 you won't have to modify your managed library to facilitate unmanaged use, which is sometimes not an option.
For me it comes down to where you want to make your code changes.
With option 2 you also have a pretty straightforward way of subsequently convert your whole application to C++/CLI to avoid the managed/unmanaged transitions that you will get. The transitions could be an issue depending on how you use your referenced assemblies i.e. getting a performance hit.
So far I have had only positive experiences with C++/CLI and can recommend going that route.
Can you run C# code from c++?
and How?
If you're C++ code is "managed" C++ that's built on the .NET common language run-time (CLR), then it's easy to reference a C# assembly and invoke public classes and methods. If, however, your C++ code is "native" (not built on the CLR), then you'll want to register your C# assembly for COM interop and invoke the COM object from your C++ code. There's an MSDN article that covers all the gory details:
http://msdn.microsoft.com/en-us/library/w29wacsy(VS.80).aspx
There's also a good article on CodeProject by Nick Parker called "Exposing .NET Components to COM" that you may find useful.
You can use unmanaged C++ to run a .NET application, but how difficult it will be will depend on which version of .NET you are using.
When I did this with .NET 2.0 it took me two solid weeks to get it working.
The answer in this page gives guidance as to which programs are needed to do this.
http://www.pcreview.co.uk/forums/thread-1225474.php
The other option that you have, depending on what you're trying to do, is to host the CLR in your application which allows you to more tightly integrate the C# code than is possible by going through COM. You can read an overview of doing this in this MSDN Magazine article.
With C++/CLI, yes (formerly Managed C++ -- which had different extensions to the language).
yes, you can use COM to call .NET
You can call .NET code without COM by using the mscoree.dll ClrCreateManagedInstance Function. You need to supply the assembly qualified name of the type name you want to create, in the pTypeName parameter.
From memory, in some cases you may need to add the ComVisible attribute to the interfaces or classes you wish to access using ClrCreateManagedInstance(). However this does not require you to also register your class or any of the other messy deployment issues that go with COM.
I'm guessing the answer that would really be useful to Chad is:
Yes, it is most definitely technically possible to run C# code from C++. However, if the other answers on this page sound like they are going over your head, then you are nowhere near experienced enough to actually do this. It is pretty difficult to pull off, all things considered, so unless you really need to be running C# code from C++, it might be best to just rewrite the C# code as C++.