Related
Background: As part of a larger assignment I need to make a C# library accessible to unmanaged C++ and C code. In an attempt to answer this question myself I have been learning C++/CLI the past few days/ weeks.
There seems to be a number of different ways to achieve using a C# dll from unmanaged C++ and C. Some of the answers in brief appear to be: using Interlope services, Using .com. and regasm, Using PInvoke (which appears to go from C# to C++ only), and using IJW in the C++/CLR (which appears to be Interlope services). I am thinking it would be best to set up a library that is perhaps a CLR wrapper that uses IJW to call my C# dll on the behalf of native C++ and C code.
Specifics: I need to pass values of string as well as int to a C# dll from c++ code, and return void.
Relevance: Many companies have many excuses to mix and match C++, C and C#. Performance: unmanaged code is usually faster, interfaces: Managed interfaces are generally easier to maintain, deploy, and are often easier on the eyes, Managers tell us too. Legacy code forces us too. It was there (Like the mountain that we climbed). While examples of how to call a C++ library from C# are abundant. Examples of how to call C# libraries from C++ code are difficult to find via Googling especially if you want to see updated 4.0+ code.
Software: C#, C++/CLR, C++, C, Visual Studio 2010, and .NET 4.0
Question details: OK multi-part question:
Is there an advantage to using com objects? Or the PInvoke? Or some other method? (I feel like the learning curve here will be just as steep, even though I do find more information on the topic in Google Land. IJW seems to promise what I want it to do. Should I give up on looking for an IJW solution and focus on this instead?) (Advantage/ disadvantage?)
Am I correct in imagining that there is a solution where I write a wrapper that that utilizes IJW in the C++/CLR? Where can I find more information on this topic, and don’t say I didn’t Google enough/ or look at MSDN without telling me where you saw it there. (I think I prefer this option, in the effort to write clear and simple code.)
A narrowing of question scope: I feel that my true issue and need is answering the smaller question that follows: How do I set up a C++/CLR library that an unmanaged C++ file can use within visual studio. I think that if I could simply instantiate a managed C++ class in unmanaged C++ code, then I might be able work out the rest (interfacing and wrapping etc.). I expect that my main folly is in trying to set up references/#includes etc. within Visual Studio, thought clearly I could have other misconceptions. Perhaps the answer to this whole thing could be just a link to a tutorial or instructions that help me with this.
Research: I have Googled and Binged over and over with some success. I have found many links that show you how to use an unmanaged library from C# code. And I will admit that there have been some links that show how to do it using com objects. Not many results were targeted at VS 2010.
References:
I have read over and over many posts. I have tried to work through the most relevant ones. Some seem tantalizingly close to the answer, but I just can’t seem to get them to work. I suspect that the thing that I am missing is tantalizingly small, such as misusing the keyword ref, or missing a #include or using statement, or a misuse of namespace, or not actually using the IJW feature properly, or missing a setting that VS needs to handle the compilation correctly, etc. So you wonder, why not include the code? Well I feel like I am not at a place where I understand and expect the code I have to work. I want to be in a place where I understand it, when I get there maybe then I'll need help fixing it. I'll randomly include two of the links but I am not permitted to show them all at my current Hitpoint level.
http://www.codeproject.com/Articles/35437/Moving-Data-between-Managed-Code-and-Unmanaged-Cod
This calls code from managed and unmanaged code in both directions going from C++ to Visual Basic and back via C++CLR, and of course I am interested in C#.: http://www.codeproject.com/Articles/9903/Calling-Managed-Code-from-Unmanaged-Code-and-vice
You can do this fairly easily.
Create an .h/.cpp combo
Enable /clr on the newly create .cpp file. (CPP -> Right click -> Properties)
Set the search path for "additional #using directories" to point towards your C# dll.
Native.h
void NativeWrapMethod();
Native.cpp
#using <mscorlib.dll>
#using <MyNet.dll>
using namespace MyNetNameSpace;
void NativeWrapMethod()
{
MyNetNameSpace::MyManagedClass::Method(); // static method
}
That's the basics of using a C# lib from C++\CLI with native code. (Just reference Native.h where needed, and call the function.)
Using C# code with managed C++\CLI code is roughly the same.
There is a lot of misinformation on this subject, so, hopefully this saves someone a lot of hassle. :)
I've done this in: VS2010 - VS2012 (It probably works in VS2008 too.)
UPDATE 2018
It seems like as if the solution does not work for Visual Studio 2017 and onwards. Unfortunately I am currently not working with Visual Studio and therefore cannot update this answer by myself. But kaylee posted an updated version of my answer, thank you!
UPDATE END
If you want to use COM, here's my solution for this problem:
C# library
First of all you need a COM compatible library.
You already got one? Perfect, you can skip this part.
You have access to the library? Make sure it's COM compatible by following the steps.
Make sure that you checked the "Register for COM interop" option in the properties of your project. Properties -> Build -> Scroll down -> Register for COM interop
The following screenshots shows where you find this option.
All the interfaces and classes that should be available need to have a GUID
namespace NamespaceOfYourProject
{
[Guid("add a GUID here")]
public interface IInterface
{
void Connect();
void Disconnect();
}
}
namespace NamespaceOfYourProject
{
[Guid("add a GUID here")]
public class ClassYouWantToUse: IInterface
{
private bool connected;
public void Connect()
{
//add code here
}
public void Disconnect()
{
//add code here
}
}
}
So that's pretty much what you have to do with your C# code. Let's continue with the C++ code.
C++
First of all we need to import the C# library.
After compiling your C# library there should be a .tlb file.
#import "path\to\the\file.tlb"
If you import this new created file to your file.cpp you can use your object as a local variable.
#import "path\to\the\file.tlb"
int _tmain(int argc, _TCHAR* argv[])
{
CoInitialize(NULL);
NamespaceOfYourProject::IInterfacePtr yourClass(__uuidof(NamespaceOfYourProject::ClassYouWantToUse));
yourClass->Connect();
CoUninitialize();
}
Using your class as an attribute.
You will noticed that the first step only works with a local variable. The following code shows how to use it as a attribute. Related to this question.
You will need the CComPtr, which is located in atlcomcli.h. Include this file in your header file.
CPlusPlusClass.h
#include <atlcomcli.h>
#import "path\to\the\file.tlb"
class CPlusPlusClass
{
public:
CPlusPlusClass(void);
~CPlusPlusClass(void);
void Connect(void);
private:
CComPtr<NamespaceOfYourProject::IInterface> yourClass;
}
CPlusPlusClass.cpp
CPlusPlusClass::CPlusPlusClass(void)
{
CoInitialize(NULL);
yourClass.CoCreateInstance(__uuidof(NamespaceOfYourProject::ClassYouWantToUse));
}
CPlusPlusClass::~CPlusPlusClass(void)
{
CoUninitialize();
}
void CPlusPlusClass::Connect(void)
{
yourClass->Connect();
}
That's it! Have fun with your C# classes in C++ with COM.
The answer from 0lli.rocks is unfortunately either outdated or incomplete. My co-worker helped me get this working, and to be frank one or two of the implementation details were not remotely obvious. This answer rectifies the gaps and should be directly copyable into Visual Studio 2017 for your own use.
Caveats: I haven't been able to get this working for C++/WinRT, just an FYI. All sorts of compile errors due to ambiguity of the IUnknown interface. I was also having problems getting this to work for just a library implementation instead of using it in the main of the app. I tried following the instructions from 0lli.rocks for that specifically, but was never able to get it compiling.
Step 01: Create your C# Library
Here's the one we'll be using for the demo:
using System;
using System.Runtime.InteropServices;
namespace MyCSharpClass
{
[ComVisible(true)] // Don't forget
[ClassInterface(ClassInterfaceType.AutoDual)] // these two lines
[Guid("485B98AF-53D4-4148-B2BD-CC3920BF0ADF")] // or this GUID
public class TheClass
{
public String GetTheThing(String arg) // Make sure this is public
{
return arg + "the thing";
}
}
}
Step 02 - Configure your C# library for COM-visibility
Sub-Step A - Register for COM interoperability
Sub-Step B - Make the assembly COM-visible
Step 3 - Build your Library for the .tlb file
You probably want to just do this as Release for AnyCPU unless you really need something more specific.
Step 4 - Copy the .tlb file into the source location for your C++ project
Step 5 - Import the .tlb file into your C++ project
#include "pch.h"
#include <iostream>
#include <Windows.h>
#import "MyCSharpClass.tlb" raw_interfaces_only
int wmain() {
return 0;
}
Step 6 - Don't panic when Intellisense fails
It will still build. You're going to see even more red-lined code once we implement the actual class into the C++ project.
Step 7 - Build your C++ project to generate the .tlh file
This file will go into your intermediate object build directory once you build the first time
Step 8 - Assess the .tlh file for implementation instructions
This is the .tlh file that is generated in the intermediate object folder. Don't edit it.
// Created by Microsoft (R) C/C++ Compiler Version 14.15.26730.0 (333f2c26).
//
// c:\users\user name\source\repos\consoleapplication6\consoleapplication6\debug\mycsharpclass.tlh
//
// C++ source equivalent of Win32 type library MyCSharpClass.tlb
// compiler-generated file created 10/26/18 at 14:04:14 - DO NOT EDIT!
//
// Cross-referenced type libraries:
//
// #import "C:\Windows\Microsoft.NET\Framework\v4.0.30319\mscorlib.tlb"
//
#pragma once
#pragma pack(push, 8)
#include <comdef.h>
namespace MyCSharpClass {
//
// Forward references and typedefs
//
struct __declspec(uuid("48b51671-5200-4e47-8914-eb1bd0200267"))
/* LIBID */ __MyCSharpClass;
struct /* coclass */ TheClass;
struct __declspec(uuid("1ed1036e-c4ae-31c1-8846-5ac75029cb93"))
/* dual interface */ _TheClass;
//
// Smart pointer typedef declarations
//
_COM_SMARTPTR_TYPEDEF(_TheClass, __uuidof(_TheClass));
//
// Type library items
//
struct __declspec(uuid("485b98af-53d4-4148-b2bd-cc3920bf0adf"))
TheClass;
// [ default ] interface _TheClass
// interface _Object
struct __declspec(uuid("1ed1036e-c4ae-31c1-8846-5ac75029cb93"))
_TheClass : IDispatch
{
//
// Raw methods provided by interface
//
virtual HRESULT __stdcall get_ToString (
/*[out,retval]*/ BSTR * pRetVal ) = 0;
virtual HRESULT __stdcall Equals (
/*[in]*/ VARIANT obj,
/*[out,retval]*/ VARIANT_BOOL * pRetVal ) = 0;
virtual HRESULT __stdcall GetHashCode (
/*[out,retval]*/ long * pRetVal ) = 0;
virtual HRESULT __stdcall GetType (
/*[out,retval]*/ struct _Type * * pRetVal ) = 0;
virtual HRESULT __stdcall GetTheThing (
/*[in]*/ BSTR arg,
/*[out,retval]*/ BSTR * pRetVal ) = 0;
};
} // namespace MyCSharpClass
#pragma pack(pop)
In that file, we see these lines for the public method we want to use:
virtual HRESULT __stdcall GetTheThing (
/*[in]*/ BSTR arg,
/*[out,retval]*/ BSTR * pRetVal ) = 0;
That means that the imported method will expect an input-string of type BSTR, and a pointer to a BSTR for the output string that the imported method will return on success. You can set them up like this, for example:
BSTR thing_to_send = ::SysAllocString(L"My thing, or ... ");
BSTR returned_thing;
Before we can use the imported method, we will have to construct it. From the .tlh file, we see these lines:
namespace MyCSharpClass {
//
// Forward references and typedefs
//
struct __declspec(uuid("48b51671-5200-4e47-8914-eb1bd0200267"))
/* LIBID */ __MyCSharpClass;
struct /* coclass */ TheClass;
struct __declspec(uuid("1ed1036e-c4ae-31c1-8846-5ac75029cb93"))
/* dual interface */ _TheClass;
//
// Smart pointer typedef declarations
//
_COM_SMARTPTR_TYPEDEF(_TheClass, __uuidof(_TheClass));
//
// Type library items
//
struct __declspec(uuid("485b98af-53d4-4148-b2bd-cc3920bf0adf"))
TheClass;
// [ default ] interface _TheClass
// interface _Object
First, we need to use the namespace of the class, which is MyCSharpClass
Next, we need to determine the the smart pointer from the namespace, which is _TheClass + Ptr ; this step is not remotely obvious, as it's nowhere in the .tlh file.
Last, we need to provide the correct construction parameter for the class, which is __uuidof(MyCSharpClass::TheClass)
Ending up with,
MyCSharpClass::_TheClassPtr obj(__uuidof(MyCSharpClass::TheClass));
Step 9 - Initialize COM and test the imported library
You can do that with CoInitialize(0) or whatever your specific COM initializer happens to be.
#include "pch.h"
#include <iostream>
#include <Windows.h>
#import "MyCSharpClass.tlb" raw_interfaces_only
int wmain() {
CoInitialize(0); // Init COM
BSTR thing_to_send = ::SysAllocString(L"My thing, or ... ");
BSTR returned_thing;
MyCSharpClass::_TheClassPtr obj(__uuidof(MyCSharpClass::TheClass));
HRESULT hResult = obj->GetTheThing(thing_to_send, &returned_thing);
if (hResult == S_OK) {
std::wcout << returned_thing << std::endl;
return 0;
}
return 1;
}
Once again, don't panic when Intellisense freaks out. You're in Black Magic, Voodoo, & Thar Be Dragons territory, so press onward!
The absolute best way I have found to do this is create a c++/cli bridge that connects the c# code to your native C++. You can do this with 3 different projects.
First Project: C# library
Second Project: C++/CLI bridge (this wraps the C# library)
Third Project: Native C++ application that uses the second project
I recently created a simple GitHub Tutorial for how to do this here. Reading through that code with a little grit and you should be able to hammer out creating a C++/CLI bridge that allows you to use C# code in your native C++.
As a bonus I added how to wrap a C# event down to a function pointer in C++ that you can subscribe to.
I found something that at least begins to answer my own question. The following two links have wmv files from Microsoft that demonstrate using a C# class in unmanaged C++.
This first one uses a COM object and regasm: http://msdn.microsoft.com/en-us/vstudio/bb892741.
This second one uses the features of C++/CLI to wrap the C# class: http://msdn.microsoft.com/en-us/vstudio/bb892742. I have been able to instantiate a c# class from managed code and retrieve a string as in the video. It has been very helpful but it only answers 2/3rds of my question as I want to instantiate a class with a string perimeter into a c# class. As a proof of concept I altered the code presented in the example for the following method, and achieved this goal. Of course I also added a altered the {public string PickDate(string Name)} method to do something with the name string to prove to myself that it worked.
wchar_t * DatePickerClient::pick(std::wstring nme)
{
IntPtr temp(ref);// system int pointer from a native int
String ^date;// tracking handle to a string (managed)
String ^name;// tracking handle to a string (managed)
name = gcnew String(nme.c_str());
wchar_t *ret;// pointer to a c++ string
GCHandle gch;// garbage collector handle
DatePicker::DatePicker ^obj;// reference the c# object with tracking handle(^)
gch = static_cast<GCHandle>(temp);// converted from the int pointer
obj = static_cast<DatePicker::DatePicker ^>(gch.Target);
date = obj->PickDate(name);
ret = new wchar_t[date->Length +1];
interior_ptr<const wchar_t> p1 = PtrToStringChars(date);// clr pointer that acts like pointer
pin_ptr<const wchar_t> p2 = p1;// pin the pointer to a location as clr pointers move around in memory but c++ does not know about that.
wcscpy_s(ret, date->Length +1, p2);
return ret;
}
Part of my question was: What is better? From what I have read in many many efforts to research the answer is that COM objects are considered easier to use, and using a wrapper instead allows for greater control. In some cases using a wrapper can (but not always) reduce the size of the thunk, as COM objects automatically have a standard size footprint and wrappers are only as big as they need to be.
The thunk (as I have used above) refers to the space time and resources used in between C# and C++ in the case of the COM object, and in between C++/CLI and native C++ in the case of coding-using a C++/CLI Wrapper. So another part of my answer should include a warning that crossing the thunk boundary more than absolutely necessary is bad practice, accessing the thunk boundary inside a loop is not recommended, and that it is possible to set up a wrapper incorrectly so that it double thunks (crosses the boundary twice where only one thunk is called for) without the code seeming to be incorrect to a novice like me.
Two notes about the wmv's. First: some footage is reused in both, don't be fooled. At first they seem the same but they do cover different topics. Second, there are some bonus features such as marshalling that are now a part of the CLI that are not covered in the wmv's.
Edit:
Note there is a consequence for your installs, your c++ wrapper will not be found by the CLR. You will have to either confirm that the c++ application installs in any/every directory that uses it, or add the library (which will then need to be strongly named) to the GAC at install time. This also means that with either case in development environments you will likely have to copy the library to each directory where applications call it.
I did a bunch of looking around and found a relatively recent article by Microsoft detailing how it can be done (there is a lot of old infomration floating around). From the article itself:
The code sample uses the CLR 4 hosting APIs to host CLR in a native C++ project, load and invoke .NET assemblies
https://code.msdn.microsoft.com/CppHostCLR-e6581ee0
Basically it describes it in two steps:
Load the CLR into a process
Load your assembly.
I have a somewhat difficult problem with rewriting a C++ application into C#. Basically the C++ application includes a C header file that contains structure and enum definitions:
Imagine it like this:
Header file:
/********** myHeader.h *************/
#ifndef MY_HEADER_H
#define MY_HEADER_H
#define MY_CONSTANT 10u
#define OTHER_CONSTANT 20u
typedef enum
{
ACTION_ONE,
ACTION_TWO,
NUMBER_OF_ACTIONS
} myEnum;
typedef struct
{
uint32_t member;
uint32_t bitfield_msb : 24;
uint32_t bitfield_lsb : 8;
} myStruct;
#endif
So currently the C++ program references these structures. It gets the format from the .h file and constructs structures based on this data. The header itself is also included in a C project. This ensures the compatibility between two projects as they both use identical data structures.
Can anybody recommend a good way of implementing this in C#? Or is it mission impossible. Ofcourse I could define the structures separately in C# format, but in that case the connection between the C project and the (C++ to be translated to C# project) would be lost.
Background: As part of a larger assignment I need to make a C# library accessible to unmanaged C++ and C code. In an attempt to answer this question myself I have been learning C++/CLI the past few days/ weeks.
There seems to be a number of different ways to achieve using a C# dll from unmanaged C++ and C. Some of the answers in brief appear to be: using Interlope services, Using .com. and regasm, Using PInvoke (which appears to go from C# to C++ only), and using IJW in the C++/CLR (which appears to be Interlope services). I am thinking it would be best to set up a library that is perhaps a CLR wrapper that uses IJW to call my C# dll on the behalf of native C++ and C code.
Specifics: I need to pass values of string as well as int to a C# dll from c++ code, and return void.
Relevance: Many companies have many excuses to mix and match C++, C and C#. Performance: unmanaged code is usually faster, interfaces: Managed interfaces are generally easier to maintain, deploy, and are often easier on the eyes, Managers tell us too. Legacy code forces us too. It was there (Like the mountain that we climbed). While examples of how to call a C++ library from C# are abundant. Examples of how to call C# libraries from C++ code are difficult to find via Googling especially if you want to see updated 4.0+ code.
Software: C#, C++/CLR, C++, C, Visual Studio 2010, and .NET 4.0
Question details: OK multi-part question:
Is there an advantage to using com objects? Or the PInvoke? Or some other method? (I feel like the learning curve here will be just as steep, even though I do find more information on the topic in Google Land. IJW seems to promise what I want it to do. Should I give up on looking for an IJW solution and focus on this instead?) (Advantage/ disadvantage?)
Am I correct in imagining that there is a solution where I write a wrapper that that utilizes IJW in the C++/CLR? Where can I find more information on this topic, and don’t say I didn’t Google enough/ or look at MSDN without telling me where you saw it there. (I think I prefer this option, in the effort to write clear and simple code.)
A narrowing of question scope: I feel that my true issue and need is answering the smaller question that follows: How do I set up a C++/CLR library that an unmanaged C++ file can use within visual studio. I think that if I could simply instantiate a managed C++ class in unmanaged C++ code, then I might be able work out the rest (interfacing and wrapping etc.). I expect that my main folly is in trying to set up references/#includes etc. within Visual Studio, thought clearly I could have other misconceptions. Perhaps the answer to this whole thing could be just a link to a tutorial or instructions that help me with this.
Research: I have Googled and Binged over and over with some success. I have found many links that show you how to use an unmanaged library from C# code. And I will admit that there have been some links that show how to do it using com objects. Not many results were targeted at VS 2010.
References:
I have read over and over many posts. I have tried to work through the most relevant ones. Some seem tantalizingly close to the answer, but I just can’t seem to get them to work. I suspect that the thing that I am missing is tantalizingly small, such as misusing the keyword ref, or missing a #include or using statement, or a misuse of namespace, or not actually using the IJW feature properly, or missing a setting that VS needs to handle the compilation correctly, etc. So you wonder, why not include the code? Well I feel like I am not at a place where I understand and expect the code I have to work. I want to be in a place where I understand it, when I get there maybe then I'll need help fixing it. I'll randomly include two of the links but I am not permitted to show them all at my current Hitpoint level.
http://www.codeproject.com/Articles/35437/Moving-Data-between-Managed-Code-and-Unmanaged-Cod
This calls code from managed and unmanaged code in both directions going from C++ to Visual Basic and back via C++CLR, and of course I am interested in C#.: http://www.codeproject.com/Articles/9903/Calling-Managed-Code-from-Unmanaged-Code-and-vice
You can do this fairly easily.
Create an .h/.cpp combo
Enable /clr on the newly create .cpp file. (CPP -> Right click -> Properties)
Set the search path for "additional #using directories" to point towards your C# dll.
Native.h
void NativeWrapMethod();
Native.cpp
#using <mscorlib.dll>
#using <MyNet.dll>
using namespace MyNetNameSpace;
void NativeWrapMethod()
{
MyNetNameSpace::MyManagedClass::Method(); // static method
}
That's the basics of using a C# lib from C++\CLI with native code. (Just reference Native.h where needed, and call the function.)
Using C# code with managed C++\CLI code is roughly the same.
There is a lot of misinformation on this subject, so, hopefully this saves someone a lot of hassle. :)
I've done this in: VS2010 - VS2012 (It probably works in VS2008 too.)
UPDATE 2018
It seems like as if the solution does not work for Visual Studio 2017 and onwards. Unfortunately I am currently not working with Visual Studio and therefore cannot update this answer by myself. But kaylee posted an updated version of my answer, thank you!
UPDATE END
If you want to use COM, here's my solution for this problem:
C# library
First of all you need a COM compatible library.
You already got one? Perfect, you can skip this part.
You have access to the library? Make sure it's COM compatible by following the steps.
Make sure that you checked the "Register for COM interop" option in the properties of your project. Properties -> Build -> Scroll down -> Register for COM interop
The following screenshots shows where you find this option.
All the interfaces and classes that should be available need to have a GUID
namespace NamespaceOfYourProject
{
[Guid("add a GUID here")]
public interface IInterface
{
void Connect();
void Disconnect();
}
}
namespace NamespaceOfYourProject
{
[Guid("add a GUID here")]
public class ClassYouWantToUse: IInterface
{
private bool connected;
public void Connect()
{
//add code here
}
public void Disconnect()
{
//add code here
}
}
}
So that's pretty much what you have to do with your C# code. Let's continue with the C++ code.
C++
First of all we need to import the C# library.
After compiling your C# library there should be a .tlb file.
#import "path\to\the\file.tlb"
If you import this new created file to your file.cpp you can use your object as a local variable.
#import "path\to\the\file.tlb"
int _tmain(int argc, _TCHAR* argv[])
{
CoInitialize(NULL);
NamespaceOfYourProject::IInterfacePtr yourClass(__uuidof(NamespaceOfYourProject::ClassYouWantToUse));
yourClass->Connect();
CoUninitialize();
}
Using your class as an attribute.
You will noticed that the first step only works with a local variable. The following code shows how to use it as a attribute. Related to this question.
You will need the CComPtr, which is located in atlcomcli.h. Include this file in your header file.
CPlusPlusClass.h
#include <atlcomcli.h>
#import "path\to\the\file.tlb"
class CPlusPlusClass
{
public:
CPlusPlusClass(void);
~CPlusPlusClass(void);
void Connect(void);
private:
CComPtr<NamespaceOfYourProject::IInterface> yourClass;
}
CPlusPlusClass.cpp
CPlusPlusClass::CPlusPlusClass(void)
{
CoInitialize(NULL);
yourClass.CoCreateInstance(__uuidof(NamespaceOfYourProject::ClassYouWantToUse));
}
CPlusPlusClass::~CPlusPlusClass(void)
{
CoUninitialize();
}
void CPlusPlusClass::Connect(void)
{
yourClass->Connect();
}
That's it! Have fun with your C# classes in C++ with COM.
The answer from 0lli.rocks is unfortunately either outdated or incomplete. My co-worker helped me get this working, and to be frank one or two of the implementation details were not remotely obvious. This answer rectifies the gaps and should be directly copyable into Visual Studio 2017 for your own use.
Caveats: I haven't been able to get this working for C++/WinRT, just an FYI. All sorts of compile errors due to ambiguity of the IUnknown interface. I was also having problems getting this to work for just a library implementation instead of using it in the main of the app. I tried following the instructions from 0lli.rocks for that specifically, but was never able to get it compiling.
Step 01: Create your C# Library
Here's the one we'll be using for the demo:
using System;
using System.Runtime.InteropServices;
namespace MyCSharpClass
{
[ComVisible(true)] // Don't forget
[ClassInterface(ClassInterfaceType.AutoDual)] // these two lines
[Guid("485B98AF-53D4-4148-B2BD-CC3920BF0ADF")] // or this GUID
public class TheClass
{
public String GetTheThing(String arg) // Make sure this is public
{
return arg + "the thing";
}
}
}
Step 02 - Configure your C# library for COM-visibility
Sub-Step A - Register for COM interoperability
Sub-Step B - Make the assembly COM-visible
Step 3 - Build your Library for the .tlb file
You probably want to just do this as Release for AnyCPU unless you really need something more specific.
Step 4 - Copy the .tlb file into the source location for your C++ project
Step 5 - Import the .tlb file into your C++ project
#include "pch.h"
#include <iostream>
#include <Windows.h>
#import "MyCSharpClass.tlb" raw_interfaces_only
int wmain() {
return 0;
}
Step 6 - Don't panic when Intellisense fails
It will still build. You're going to see even more red-lined code once we implement the actual class into the C++ project.
Step 7 - Build your C++ project to generate the .tlh file
This file will go into your intermediate object build directory once you build the first time
Step 8 - Assess the .tlh file for implementation instructions
This is the .tlh file that is generated in the intermediate object folder. Don't edit it.
// Created by Microsoft (R) C/C++ Compiler Version 14.15.26730.0 (333f2c26).
//
// c:\users\user name\source\repos\consoleapplication6\consoleapplication6\debug\mycsharpclass.tlh
//
// C++ source equivalent of Win32 type library MyCSharpClass.tlb
// compiler-generated file created 10/26/18 at 14:04:14 - DO NOT EDIT!
//
// Cross-referenced type libraries:
//
// #import "C:\Windows\Microsoft.NET\Framework\v4.0.30319\mscorlib.tlb"
//
#pragma once
#pragma pack(push, 8)
#include <comdef.h>
namespace MyCSharpClass {
//
// Forward references and typedefs
//
struct __declspec(uuid("48b51671-5200-4e47-8914-eb1bd0200267"))
/* LIBID */ __MyCSharpClass;
struct /* coclass */ TheClass;
struct __declspec(uuid("1ed1036e-c4ae-31c1-8846-5ac75029cb93"))
/* dual interface */ _TheClass;
//
// Smart pointer typedef declarations
//
_COM_SMARTPTR_TYPEDEF(_TheClass, __uuidof(_TheClass));
//
// Type library items
//
struct __declspec(uuid("485b98af-53d4-4148-b2bd-cc3920bf0adf"))
TheClass;
// [ default ] interface _TheClass
// interface _Object
struct __declspec(uuid("1ed1036e-c4ae-31c1-8846-5ac75029cb93"))
_TheClass : IDispatch
{
//
// Raw methods provided by interface
//
virtual HRESULT __stdcall get_ToString (
/*[out,retval]*/ BSTR * pRetVal ) = 0;
virtual HRESULT __stdcall Equals (
/*[in]*/ VARIANT obj,
/*[out,retval]*/ VARIANT_BOOL * pRetVal ) = 0;
virtual HRESULT __stdcall GetHashCode (
/*[out,retval]*/ long * pRetVal ) = 0;
virtual HRESULT __stdcall GetType (
/*[out,retval]*/ struct _Type * * pRetVal ) = 0;
virtual HRESULT __stdcall GetTheThing (
/*[in]*/ BSTR arg,
/*[out,retval]*/ BSTR * pRetVal ) = 0;
};
} // namespace MyCSharpClass
#pragma pack(pop)
In that file, we see these lines for the public method we want to use:
virtual HRESULT __stdcall GetTheThing (
/*[in]*/ BSTR arg,
/*[out,retval]*/ BSTR * pRetVal ) = 0;
That means that the imported method will expect an input-string of type BSTR, and a pointer to a BSTR for the output string that the imported method will return on success. You can set them up like this, for example:
BSTR thing_to_send = ::SysAllocString(L"My thing, or ... ");
BSTR returned_thing;
Before we can use the imported method, we will have to construct it. From the .tlh file, we see these lines:
namespace MyCSharpClass {
//
// Forward references and typedefs
//
struct __declspec(uuid("48b51671-5200-4e47-8914-eb1bd0200267"))
/* LIBID */ __MyCSharpClass;
struct /* coclass */ TheClass;
struct __declspec(uuid("1ed1036e-c4ae-31c1-8846-5ac75029cb93"))
/* dual interface */ _TheClass;
//
// Smart pointer typedef declarations
//
_COM_SMARTPTR_TYPEDEF(_TheClass, __uuidof(_TheClass));
//
// Type library items
//
struct __declspec(uuid("485b98af-53d4-4148-b2bd-cc3920bf0adf"))
TheClass;
// [ default ] interface _TheClass
// interface _Object
First, we need to use the namespace of the class, which is MyCSharpClass
Next, we need to determine the the smart pointer from the namespace, which is _TheClass + Ptr ; this step is not remotely obvious, as it's nowhere in the .tlh file.
Last, we need to provide the correct construction parameter for the class, which is __uuidof(MyCSharpClass::TheClass)
Ending up with,
MyCSharpClass::_TheClassPtr obj(__uuidof(MyCSharpClass::TheClass));
Step 9 - Initialize COM and test the imported library
You can do that with CoInitialize(0) or whatever your specific COM initializer happens to be.
#include "pch.h"
#include <iostream>
#include <Windows.h>
#import "MyCSharpClass.tlb" raw_interfaces_only
int wmain() {
CoInitialize(0); // Init COM
BSTR thing_to_send = ::SysAllocString(L"My thing, or ... ");
BSTR returned_thing;
MyCSharpClass::_TheClassPtr obj(__uuidof(MyCSharpClass::TheClass));
HRESULT hResult = obj->GetTheThing(thing_to_send, &returned_thing);
if (hResult == S_OK) {
std::wcout << returned_thing << std::endl;
return 0;
}
return 1;
}
Once again, don't panic when Intellisense freaks out. You're in Black Magic, Voodoo, & Thar Be Dragons territory, so press onward!
The absolute best way I have found to do this is create a c++/cli bridge that connects the c# code to your native C++. You can do this with 3 different projects.
First Project: C# library
Second Project: C++/CLI bridge (this wraps the C# library)
Third Project: Native C++ application that uses the second project
I recently created a simple GitHub Tutorial for how to do this here. Reading through that code with a little grit and you should be able to hammer out creating a C++/CLI bridge that allows you to use C# code in your native C++.
As a bonus I added how to wrap a C# event down to a function pointer in C++ that you can subscribe to.
I found something that at least begins to answer my own question. The following two links have wmv files from Microsoft that demonstrate using a C# class in unmanaged C++.
This first one uses a COM object and regasm: http://msdn.microsoft.com/en-us/vstudio/bb892741.
This second one uses the features of C++/CLI to wrap the C# class: http://msdn.microsoft.com/en-us/vstudio/bb892742. I have been able to instantiate a c# class from managed code and retrieve a string as in the video. It has been very helpful but it only answers 2/3rds of my question as I want to instantiate a class with a string perimeter into a c# class. As a proof of concept I altered the code presented in the example for the following method, and achieved this goal. Of course I also added a altered the {public string PickDate(string Name)} method to do something with the name string to prove to myself that it worked.
wchar_t * DatePickerClient::pick(std::wstring nme)
{
IntPtr temp(ref);// system int pointer from a native int
String ^date;// tracking handle to a string (managed)
String ^name;// tracking handle to a string (managed)
name = gcnew String(nme.c_str());
wchar_t *ret;// pointer to a c++ string
GCHandle gch;// garbage collector handle
DatePicker::DatePicker ^obj;// reference the c# object with tracking handle(^)
gch = static_cast<GCHandle>(temp);// converted from the int pointer
obj = static_cast<DatePicker::DatePicker ^>(gch.Target);
date = obj->PickDate(name);
ret = new wchar_t[date->Length +1];
interior_ptr<const wchar_t> p1 = PtrToStringChars(date);// clr pointer that acts like pointer
pin_ptr<const wchar_t> p2 = p1;// pin the pointer to a location as clr pointers move around in memory but c++ does not know about that.
wcscpy_s(ret, date->Length +1, p2);
return ret;
}
Part of my question was: What is better? From what I have read in many many efforts to research the answer is that COM objects are considered easier to use, and using a wrapper instead allows for greater control. In some cases using a wrapper can (but not always) reduce the size of the thunk, as COM objects automatically have a standard size footprint and wrappers are only as big as they need to be.
The thunk (as I have used above) refers to the space time and resources used in between C# and C++ in the case of the COM object, and in between C++/CLI and native C++ in the case of coding-using a C++/CLI Wrapper. So another part of my answer should include a warning that crossing the thunk boundary more than absolutely necessary is bad practice, accessing the thunk boundary inside a loop is not recommended, and that it is possible to set up a wrapper incorrectly so that it double thunks (crosses the boundary twice where only one thunk is called for) without the code seeming to be incorrect to a novice like me.
Two notes about the wmv's. First: some footage is reused in both, don't be fooled. At first they seem the same but they do cover different topics. Second, there are some bonus features such as marshalling that are now a part of the CLI that are not covered in the wmv's.
Edit:
Note there is a consequence for your installs, your c++ wrapper will not be found by the CLR. You will have to either confirm that the c++ application installs in any/every directory that uses it, or add the library (which will then need to be strongly named) to the GAC at install time. This also means that with either case in development environments you will likely have to copy the library to each directory where applications call it.
I did a bunch of looking around and found a relatively recent article by Microsoft detailing how it can be done (there is a lot of old infomration floating around). From the article itself:
The code sample uses the CLR 4 hosting APIs to host CLR in a native C++ project, load and invoke .NET assemblies
https://code.msdn.microsoft.com/CppHostCLR-e6581ee0
Basically it describes it in two steps:
Load the CLR into a process
Load your assembly.
My problem is , i have some functions in a DLL some of these functions are for example :
#include <string>
using namespace std;
extern "C" __declspec(dllexport) string __cdecl encryption(string s)
{
return s;
}
Whenever i try to call this function from C# , here is the code im using :
[DllImport("Packer.dll", EntryPoint = "encryption")]
static extern string encryption(string s);
i get an error :
A call to PInvoke function 'Packer' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.
im guessing i get this error because i dont have the right declarations for the function
can anyone guide me how to fix that , thanks in advance
std::string can not be used with PInvoke, because C++ does not have an ABI for its objects which is required to properly clean stack, copy objects, etc. This is one of the greatest pains of C++.
You have to use char* pointers and plain C APIs. Simply put, PInvoke does not work with C++.
As I'm sure you already know, the C++ std::string is actually a template. Only when the template is instantiated (as std::basic_string<char> in this case), the exact layout of the objects of that type and signatures of the methods are determined by the C++ compiler.
Unfortunately, only the C++ compiler in question has the access to all the relevant information (such as template source code) to make these kinds of decisions. That's why non-C features such as templates are generally not "transferable" even between different C++ compilers, let alone C++ and C#.
Also, C++ names are typically "mangled" in a C++ compiler-specific manner.
You'll have to change the signature of your native method, so it is becomes a "pure" C function:
Ensure there is no C++ name mangling by declaring the function as extern "C" (you are already doing that).
Use char* parameter instead of std::string.
Return char* result instead of std::string, but be very careful how you do it.
Ensure your DllImportAttribute.CallingConvention matches the __cdecl, __stdcall or __fastcall in your C.
The problem here is, you're using the STL string class which C# doesn't know how to marshal. You have two options here:
refactor your C++ code to work with char * buffers. Or write a wrapper or an overload or something that uses char * instead of string.
Write a C++/CLI wrapper around your C++ functions that uses System::String and calls the STL string versions internally.
If memory serves, if you don't specify otherwise P/Invoke assumes the calling convention is __stdcall. If so, changing your __cdecl to __stdcall should fix the first problem.
As #Adam Rosenfield points out, you probably also need to pass and return a char const *, not a string. C# and C++ almost certainly have somewhat different ideas of what constitutes a string.
I have a C++ console Exe which does some progamming. Now i wanted to write a C# GUI which does some of the programming that the C++ exe does. I was thinking of few approaches,
Write the C# GUI with all programming in C++ done from scratch.(I do not want to do this for the amount of rework it entails)
Build a C++ dll which does the programming and have it imported in GUI app.(Now here i have a concern. How do i capture the output of the routines in c++ dll and display it in GUI? Should i return the output as string for every routine that the app calls.? Since i dont know managed c++ iam going to build an unmanaged C++ dll. )
Building a C++/CLI dll really isn't that hard. You basically use unmanaged C++ code except that you define a "public ref class" which hosts the functions you want the C# code to see.
What kind of data are you returning? Single numbers, matrices of numbers, complex objects?
UPDATE: Since it has been clarified that the "output" is iostreams, here is a project demonstrating redirection of cout to a .NET application calling the library. Redirecting clog or cerr would just require a handful of additional lines in DllMain patterned after the existing redirect.
The zip file includes VS2010 project files, but the source code should also work in 2005 or 2008.
The iostreams capture functionality is contained in the following code:
// compile this part without /clr
class capturebuf : public std::stringbuf
{
protected:
virtual int sync()
{
// ensure NUL termination
overflow(0);
// send to .NET trace listeners
loghelper(pbase());
// clear buffer
str(std::string());
return __super::sync();
}
};
BOOL WINAPI DllMain(_In_ HANDLE _HDllHandle, _In_ DWORD _Reason, _In_opt_ LPVOID _Reserved)
{
static std::streambuf* origbuf;
static capturebuf* altbuf;
switch (_Reason)
{
case DLL_PROCESS_ATTACH:
origbuf = std::cout.rdbuf();
std::cout.rdbuf(altbuf = new capturebuf());
break;
case DLL_PROCESS_DETACH:
std::cout.rdbuf(origbuf);
delete altbuf;
break;
}
return TRUE;
}
// compile this helper function with /clr
void loghelper(char* msg) { Trace::Write(gcnew System::String(msg)); }
So you just want to call c++ library from managed .net code?
Then you would need to either build a COM object or a p-invokable library in c++. Each approach has it's own pros and cons depending on your business need. You would have to marshall data in your consumer. There are tons and tons of material on both concepts.
Possibly relevant: Possible to call C++ code from C#?
You could just write a C# GUI wrapper (as you suggest in option 2) and spawn the C++ process; however, this will be a little slow (I don't know if that matters).
To run your C++ exe and capture the output you can use the ProcessRunner I put together. Here is the basic usage:
using CSharpTest.Net.Processes;
partial class Program
{
static int Main(string[] args)
{
ProcessRunner run = new ProcessRunner("svn.exe", "update");
run.OutputReceived += new ProcessOutputEventHandler(run_OutputReceived);
return run.Run();
}
static void run_OutputReceived(object sender, ProcessOutputEventArgs args)
{
Console.WriteLine("{0}: {1}", args.Error ? "Error" : "Output", args.Data);
}
}
See the first comment in this page to redirect stderr
Probably the best way to go here is use P/Invoke or Platform Invoke. Depending on the structure or your C++ dll interface you may want to wrap it in a pure C interface; it is easiest if your interface uses only blittable types. If you limit your dll interface to blittable types (Int32, Single, Boolean, Int32[], Single[], Double[] - the basics) you will not need to do any complex marshaling of data between the managed (C#) and unmanaged (C) memory spaces.
For example, in your c# code you define the available calls in your C/C++ dll using the DllImport attribute.
[DllImport, "ExactDllName.dll"]
static extern boolean OneOfMyCoolCRoutines([In] Double[] x, [In] Double[] y, [Out] Double result)
The little [In]'s and [Out]'s are not strictly required, but they can speed things along. Now having added your "ExactDllName.dll" as a reference to your C# project, you can call your C/C++ function from your C# code.
fixed(Double *x = &x[0], *y = &y[0] )
{
Boolean returnValue = OneOfMyCoolCRoutines(x, y, r);
}
Note that I'm essentially passing pointers back and fourth between my dll and C# code. That can cause memory bugs because the locations of those arrays may be changed by the CLR garbage collector, but the C/C++ dll will know nothing of it. So to guard against that, I've simply fixed those pointers in my C#, and now they won't move in memory while my dll is operating on those arrays. This is now unsafe code and I'll need to compile my C# code w/ that flag.
There are many fine details to language interop, but that should get you rolling. Sticking to a stateless C interface of blittable types is a great policy if possible. That will keep your language interop code the cleanest.
Good luck,
Paul