I have a C# apllication having add-ons capability. An add-on/plug-in that implements a specific interface can be linked/loaded at runtime to the main C# application.
Now to my question: how can I develop an unmanaged cpp dll that implements the C# interface and be loaded runtime to the C# app?
Thanks,
Cabbi
You can implement interface using p/inkove, for example:
public interface IDirectory
{
bool IsDirectoryEmplty(string path);
}
public class Directory : IDirectory
{
[DllImport("Shlwapi.dll", EntryPoint = "PathIsDirectoryEmpty")]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool IsDirectoryEmplty([MarshalAs(UnmanagedType.LPStr)]string directory);
bool IInterface.IsDirectoryEmplty(string path)
{
return IsDirectoryEmplty(path);
}
}
With common language support on, you can write managed dll with full native c++ capability mixed in.
And you can load unmanaged dll via PInvoke in .Net, but I'd rather not recommend that way.
Strictly speaking, you cannot have an unmanaged DLL that implements a C# (managed) interface.
However, you can create a mixed mode assembly, that might be what you want. This is a very common way to provide a native C++ (unmanaged) implementation with a .NET wrapper making it an assembly that looks managed to a C# (or other .NET language) consumer.
In addition, you can use PInvoke to consume a pure native DLL from a NET assembly.
Related
How to call managed c# functions from unmanaged c++
Or use a project of mine that allows C# to create unmanaged exports. Those can be consumed as if they were written in a native language.
I used COM interop first, but by now I switched to IJW (it just works), as it is a lot simpler. I have a wrapper C++/CLR DLL (compile with /clr).
A simple example (using statics to make the calls easier):
namespace MyClasses
{
public class MyClass
{
public static void DoSomething()
{
MessageBox.Show("Hello World");
}
}
}
In the DLL I can reference namespaces as follows:
using namespace MyClasses;
And call it:
__declspec(dllexport) void CallManagedCode()
{
MyClass::DoSomething();
}
Now you have an unmanaged DLL export "CallManagedCode" which calls into the managed code.
Of course, you also have to convert data between the managed/unmanaged boundary. Starting with VS2008, Microsoft includes a marshal-helper for converting between unmanaged and managed types. See http://msdn.microsoft.com/en-us/library/bb384865.aspx
I used C++/CLI wrapper classes described here and it was relatively easy to implement.
RE: How to call managed C# code from an unmanaged C++ application?
http://www.tech-archive.net/Archive/DotNet/microsoft.public.dotnet.framework.interop/2005-05/msg00030.html
Calling Managed .NET C# COM Objects from Unmanaged C++ Code ...
http://www.codeproject.com/KB/cs/ManagedCOM.aspx
Wrapping a managed C# DLL in a unmanaged C++ project : dll .
http://www.experts-exchange.com/Programming/Languages/.NET/Q_22006727.html
I have a plugin written for a C++ program (as a .dll). The interface this .dll relies on is something like the following:
class Platform
{
virtual bool callSomeFunc() = 0;
//etc.
}
The .dll provides the platform with an object through an extern "C" function. Pretty standard. The .dll can interact with the platform via an object of a class implementing the above interface. Pretty standard I guess.
Now we have a need to write the platform in C#. Ideally without rewriting the plugin because we have most of our code in plugin. Is there a way to go about this? (Something like passing a C# object for the Platform object the .dll expects?)
If you wish to implement an object in the C# code that the unmanaged code can use, then you can no longer use a C++ class. Only C++ code can create C++ classes. C# code cannot.
The obvious thing to do is to use COM for your interop. The C# code can both implement and consume COM objects.
I want to use rasterbar libtorrent in a C# application. It's written in unmanaged C++.
I'm new at using DLLs and found this article online: How to Marshal a C++ Class
It describes that it's not possible to marshal/invoke a C++ class directly and you have to write a bridge in C (or managed C++) in order to use the library in managed C# code.
The article is from 2007 and I wonder if there is a better solution to use C++ DLLs by now. I'm looking for solutions that also work on the Mono platform. libtorrent is cross plattform so it should be possible.
First you should have the libtorrent dll built for windows. This link here can help you. Then for calling the un-managed code (C++ in this case) from the managed code (C# in this case) you can use Platform Invocation Services (PInvoke). It allows managed code to call unmanaged functions that are implemented in a DLL. For example have a look on this MSDN code
// PInvokeTest.cs
using System;
using System.Runtime.InteropServices;
class PlatformInvokeTest
{
[DllImport("msvcrt.dll")]
public static extern int puts(string c);
[DllImport("msvcrt.dll")]
internal static extern int _flushall();
public static void Main()
{
puts("Test");
_flushall();
}
}
The better approach will be to write a wrapper class in C# for libtorrent dll, wrap it's methods using PInvoke and use the wrapper throughout your project.
I have following problem statement.
Export a C++ class in the dll (un-managed).
Create and use an object of this class in C# code.
For the first part I have the classDLL.h as follows
``
#include <iostream>
__declspec(dllexport)
class pABC{
private:
int x;
public:
void func();
};
The respective cpp is also there. On compiling I get the dll.For thesecond part of the problem I am not getting how to proceed.
Thanks.
You can't access an unmanaged class directly from C# code. You can write a small wrapper .DLL in C++/CLI, which wraps the unmanaged class in a managed class which is visible to C#.
Convert the C++ class and DLL to be COM. If you don't have access to the unmanaged code source or can't modify, you can implement a COM wrapper class in a different DLL that consumes the original DLL and proxies the functionality of the original class through a COM class.
Define an interface in an IDL file to represent your C++ class (along with a coclass declaration). Use only basic COM types in all methods (BSTR for strings, HRESULT for return codes). Complicated structs passed as params should be refactored into their own interface.
Build your COM DLL such that it outputs a type library (tlb file).
Implement the interface (including IUnknown methods) in your C++ class. Build the COM DLL and register it.
Import the type library into your C# project. Or use the type library importer. You should now be able to instantiate your C++ class (through COM) via "new".
By the way, ATL is a great framework to get going on this quickly.
Google P/Invoke or see www.pinvoke.net
[DllImport("pABC.dll", SetLastError = true, CharSet = CharSet.Auto)]
private static extern void func();
I have couple of lib files and I want to use in my project. How to build the C# Wrapper around C++ lib files.
Any weblink or any tutorial you know, please send me.
Thanks in advance.
Harsha
Create a C++ CLR Class Library project, and then write a C++/CLI class which wraps the functions in your libs.
From C#, you can then add a reference to your class library, and call the class and its methods directly.
After creating the C++ CLR class library.
You can also consume it using DLLImport
//c# code
[DllImport(#CPPProjectName, CallingConvention = CallingConvention.StdCall)]
public static extern void SendData(string args);
Invoke the method in normal way
SendData("data123");