Do I have to create a C# DLL to call C++ DLL or I can call it directly from my C# application?
You can call it directly with PInvoke and the DllImport attribute. Assuming, of course, that it has standard C entry points, not compiler-specific C++ entry points.
Unless you were talking about C++/CLI, in which case you would reference the .NET DLL exactly as you would reference any other .NET DLL.
You can call a Win32 navite dll directly from your code using P/Invoke.
http://msdn.microsoft.com/en-us/magazine/cc164123.aspx
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I am new to Visual Studio 2010,
I have the DLL written with C# , and it is working with VB.NET , Now I want to use it with VC++, Can you help me ?
If you are planning on using .NET extensions in your VC++ project, you just need to add a reference to your C# DLL in your VC++ project.
If you're planning to use pure C++, you'll need to change your C# DLL to be COM-Visible, and generate a typelib that you'll import in your C++ project.
You can access functions from native DLL (written in C++) from .NET using PInvoke. To use managed DLL from native code (eg. call C# method from C++ code) you have to wrap managed code in COM component and use that COM object from C++
Going the other way is easy using P/invoke. Calling managed code from unmanaged is tricker. One good option is COM, but there is an alternative. Robert Giesecke has published an excellent project that allows you to expose managed methods as unmanaged DLL exports.
It's very simple to use. You simply download the Visual Studio template, create a project based on that, add your code, and mark exports with the DllExport attribute.
Or you can create Manager C++ DLL that will reference and implement all or custom objects from C# DLL.
After than you can create dllexport methods in your MCPP DLL.
And then you can access C# DLL thru MCPP DLL using LoadLibrary(...)/GetProcAddress(...) methods.
Example:
using namespace System;
using namespace System::Windows::Forms;
__declspec(dllexport) LPVOID GetPluginInterface()
{
return (IWithExecuteCommandMethod*)&theApp;
}
bool CClass::ExecuteCommand()
{
if(Threading::Thread::CurrentThread->TrySetApartmentState(System::Threading::ApartmentState::STA))
{
Flatbed::SomeDialog ^pDialog=gcnew Flatbed::SomeDialog();
pDialog->ShowDialog();
}
else
{
Threading::Thread ^pDialog=gcnew Threading::Thread(gcnew Threading::ThreadStart(ThreadProc));
pDialog->SetApartmentState(Threading::ApartmentState::STA);
pDialog->Start();
}
return false;
}
I have windows form application written in VC ++ . I want to change the button click in this app (WInform app in VC++) to hit a function written in C#.
What are the possible ways to do this.
Calling a C# assembly without compiling with C++/CLI is tricky. some of the ideas I've had:
a) Create a mixed-assembly wrapper dll (mixed assemblies contain both native code and managed code). Add a reference to your C# assembly, then create functions in your dll that call the C# code via C++/CLI, then define dll entrypoints ( __declspec(dllexport) ) for those functions. You can now link against the dll as it will provide a native interface that C++ can understand, while internally that dll can call your C# code.
( Afterthought: You can probably compile this to a .lib, that would be easier than a dll.)
Walkthrough: Creating and Using a Static Library
b) Use Mono to call the C# assembly. Mono has a C API which you can use to load and use managed assemblies without using c++/CLI. This is what I would do if C++/CLI is not an option.
Embedding Mono
c) If your function has a relatively simple input/output signature (no large objects, etc) you might consider compiling your C# function into an executable and use standard input/output to call the function. You'll have to carry input arguments and the output as text, though. Then make C++ start the executable and pass some input to it, and read the output.
I'm trying to use the lame_enc.dll file from LAME in a C# project, but adding the thing seems impossible.
I keep getting an error that says that a reference could not be added and to please check if the is accessible, a valid assembly or COM component.
I have no C++ experience, though I would like to use the functionality. Right now I'm using Process from the .NET framework to call lame.exe and do stuff, but I'd like to know if there's another way.
You can only add managed assemblies as a reference to a managed project. What I normally do in this situation is to add it as ressource instead with "copy local" settings. That way the DLL is tied to and deployed with your project. I then use DllImport to manually get the APIs I need from that DLL.
You have to use P/Invoke to call unmanaged APIs from managed code.
To use an unmanaged dll (native C++) in C#, you have to use DllImport, not adding a reference to the project in visual studio (and that is why you get an error).
Here is the documentation of DllImport from the MSDN.
You will need to use PInvoke to call functions in your native lame dll. However, you will only be able to call functions that have been exported as "C" style.
You can use a tool like "PInvoke Interop Assistant" that will help you when working out the PInvoke call signatures to make calls from C# to your native dll:
http://clrinterop.codeplex.com/releases/view/14120
I am wrote a visual c++ win32 console app, and i wrote it and tested it in
win32 console project
. then i switch to
win32 project
and imported all the source files and created a dll for it. by mark the class i want to export as
#define DllExport __declspec( dllexport )
class DllExport theClass {
}
it works and the dll is generated. then i created a another c# project and want to add the dll to the project. by reference->add reference-> browser. then i select that dll.
then it is gives me an error
a reference to the '''''''.dll could
not be added. please make sure that
the file is accessible, and that is a
valid assembly or com component.
anyone knows where i did wrong to generate/import the dll?
thanks
The Add Reference dialog can only work for DLLs that contain metadata (managed code) or a type library (a COM server). Your DLL doesn't fit that bill, you can only use the [DllImport] attribute in C# code to use the P/Invoke marshaller to call an unmanaged DLL entrypoint.
That can not be a native C++ class, like you are trying to do, there is no reliable mechanism for managed code to allocate unmanaged memory and call the constructor (and destructor) of a native C++ class. Short from the difficulty of finding the constructor and destructor code, there is no way for the P/Invoke marshaller to know the size of the object. The C++ language doesn't generate the metadata necessary to know this required information.
If you want to pursue P/Invoke then write an plain global function, decorated with extern "C", __declspec(dllexport) and (optionally) __stdcall.
If you want to export a C++ class then the only avenue is using the C++/CLI language and write a "ref class" wrapper for the native C++ class.
Or you could write a COM coclass, the universal glue in Windows. Very well supported by .NET, probably not something you want to pursue if you never wrote COM code before. ATL is the best way to get one going.
I have a C++ DLL that needs to call a function (pass a value, return a value) in a C# class library.
Is my only option to give the C# DLL a COM interface and call it from C++ with IDispatch?
Is this the best method?
Couple of options available for you here
Use a mixed mode C++/CLI assembly as a bridge between the C++ and C# DLL
Use the a COM bridge by exposing several of the key C# types as COM objects. This can then be accessed via the C++ code by normal COM semantics
This project Creates dll exports for static methods in classes. You could then call a C# static method from unmanaged code.
One approach that would work would be to call it though COM. You can use the Regasm tool to create the COM wrapper.
It's not the only option.
You could also compile your C++ DLL as a managed DLL.
You could host your C# DLL as a service and remote into it.