I am trying to call my C++ library from my C# application (via C++/CLI). I followed the example from this question (for my specific application). The setup of my application is:
Project1: C++ Project (I compile this to a DLL)
Project2: C++ Project (my CLR wrapper; just the header file per the example above; references Project1)
Project3: C# Project (references Project2)
Unfortunately, when I actually go to access the CLR wrapper object in my C# application, I receive the following error:
The type or namespace name 'YourClass'
could not be found (are you missing a
using directive or an assembly
reference?)
Do I have the project setup incorrectly, or is there something else I should be looking into? (Unfortunately, I cannot post the code for proprietary reasons, but it is a very simple bit of code and easily follows the above example.)
Update:
So I did exactly what Chris said to do (see answer below), but I am still receiving a message from my C# application that "The type or namespace name 'MyProgram' could not be found (are you missing a using directive or an assembly reference?). Here is a (mock-up) of my code.
Project1 - This is my C++ application. It compiles/works. I have used it elsewhere. (I get a DLL out of this build.)
Project2 - Here is my code for my wrapper.
MyWrapper.h
#pragma once
#include "myorigapp.h"
using namespace System;
namespace MyProgram
{
public ref class MyWrapper
{
private:
myorigapp* NativePtr;
public:
MyWrapper()
{
NativePtr = new myorigapp();
}
~MyWrapper()
{
delete NativePtr;
NativePtr = NULL;
}
void dostuff()
{
NativePtr->dostuff();
}
}
}
Project3 - This is my C# application.
Program.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MyProgram;
namespace Testing
{
class Program
{
static void Main(string[] args)
{
MyWrapper p = new MyWrapper();
p.dostuff();
}
}
}
Project3 references Project2 which references Project1. Everything builds without errors (except the error I described above in the C# code on the using MyProgram line).
Just including the header from a pure C++ application isn't good enough. You need to wrap your unmanaged objects with managed ones in Project2 (i.e. public ref class YourClassDotNet)
#include "YourHeader.h"
namespace MyManagedWrapper
{
public ref class YourClassDotNet
{
private:
YourClass* ptr;
public:
YourClassDotNet()
{
ptr = new YourClass();
}
~YourClassDotNet()
{
this->!YourClassDotNet();
}
!YourClassDotNet()
{
delete ptr;
ptr = NULL;
}
void SomeMethod()
{
ptr->SomeMethod();
}
}
}
Okay, well, I now feel dumb.
It turns out that the problem I was having (which I solved a couple weeks ago - just got around to updating this answer) was that I had included the header file (see Chris' answer for that), but I hadn't actually included the CPP file (which is empty other than including the header file).
Once I did this, the DLL compiled correctly and I could call the C++ functions (using C++/CLI) from my C# code.
Chris showed you the way to create a managed class that uses unmanaged code inside. There is a lot of that that you can do in C# using unsafe (it's just that hardly anyone does).
However, the reverse is also possible: using .NET types directly from a native type/function.
The thing to watch out for is that any managed pointer has to be marked as such. For this purpose, C++/CLI defines a special type of smartpointer gcroot<T> (mimicking boost::shared_pointer or std::auto_ptr in a way). So to store a managed string inside your C++ class, use the following:
#include <string>
#include <vcclr.h>
using namespace System;
class CppClass {
public:
gcroot<String^> str; // can use str as if it were String^
CppClass(const std::string& text) : str(gcnew String(text.c_str())) {}
};
int main() {
CppClass c("hello");
c.str = gcnew String("bye");
Console::WriteLine( c.str ); // no cast required
}
Note that (if it hasn't been fixed these days) you'll run into a bit of friction with the mismatch between managed null and C/C++ NULL.
You can't easily type, as you would expect:
gcroot<Object^> the_thing;
...
if (the_thing != nullptr)
...
}
Instead you'd have to use the native style (the smart wrapper gcroot handles this)
gcroot< Object^ > the_thing;
if ( the_thing != NULL ) {} // or equivalently...
if ( the_thing ) {}
// not too sure anymore, but I thought the following is also possible:
if ( the_thing != gcroot<Object>(nullptr) ) {}
Note: I don't have access to a windows machine anywhere near these days, so I've quoted from memory
Related
I am doing a POC where I need to invoke a c# method from a c++ application.
So I did the following:
Create a c# library.
Create a c++/cli library wrapping the dll from step 1.
Creating a c++ library that would consume cli wrapper.
Creating an unmanaged console application that would use c++ dll output from step 3.
Guys,
I have done a lot of searches in last days but did not get any useful help.
Created the c# project with output: DotNetLogger.dll
Created the c++/cli project with output: CliLogger.dll
Also referenced DotNetLogger.dll
Also exported a method.
Create C++ project with output CppLogger.dll
and so on.
Also,
C# project setting: v4.6.2
C++/CLI project settings: /CLR enabled with v4.6.2
C++ project setting: no /clr
namespace DotNetLogger
{
public class ManagedLogger
{
public void Ping()
{
//Do something
}
}
}
using namespace System;
using namespace DotNetLogger;
namespace CliLogger {
public ref class LoggerBridge
{
public:
ManagedLogger^ obj;
LoggerBridge() {
obj = gcnew ManagedLogger();
}
void Result() {
return obj->Ping();
}
};
}
__declspec(dllexport) void AreYouThere() {
CliLogger::LoggerBridge obj;
return obj.Result();
}
#pragma once
#include "D:\Logger_POC_NoWorks\InteropLogger\CliLogger\CliLogger.h"
__declspec(dllimport) void AreYouThere();
class UnmanagedLogger {
public:
void InvokeResult() {
return AreYouThere();
}
};
#include "pch.h"
#include <iostream>
#include "D:\Logger_POC_NoWorks\InteropLogger\CppLogger\CppLogger.h"
int main()
{
UnmanagedLogger uLogger;
uLogger.InvokeResult();
}
Expected Result:
The console application shall build successfully in VS 2017.
But I am getting compiler errors;
Warning C4273 'AreYouThere': inconsistent dll linkage ServiceCode d:\logger_poc_noworks\interoplogger\cpplogger\cpplogger.h 5
Error C2871 'DotNetLogger': a namespace with this name does not exist ServiceCode d:\logger_poc_noworks\interoplogger\clilogger\clilogger.h 4
Error C2039 'LoggerBridge': is not a member of 'CliLogger' ServiceCode d:\logger_poc_noworks\interoplogger\clilogger\clilogger.h 21
And many cascading errors.
I'm guessing your second block of code is clilogger.h?
You don't need to include cliLogger.h in your 3rd block of code as you are only using AreYouThere which you have already declared, this declaration also conflicts with the declaration from the header (hence the inconsistent dll linkage warning). This header also contains CLI code which will produce errors in your pure c++ file (probably the cause of your 'LoggerBridge': is not a member of 'CliLogger' error).
The #include directive is resolved by the pre-processor, which just is a pure text processor unaware of actual C++ (or C) semantics. So this piece of code
#include "D:\Logger_POC_NoWorks\InteropLogger\CliLogger\CliLogger.h"
__declspec(dllimport) void AreYouThere();
class UnmanagedLogger { /* ... */ }
will result in
using namespace System;
using namespace DotNetLogger;
namespace CliLogger { /* ... */ }
__declspec(dllexport) void AreYouThere()
{
CliLogger::LoggerBridge obj;
return obj.Result();
}
__declspec(dllimport) void AreYouThere();
class UnmanagedLogger { /* ... */ }
being presented to compiler after pre-processing, which will result in two problems:
Unmanaged compiler still sees managed code (e. g. public ref class LoggerBridge, which is invalid in pure unmanaged C++).
You get the incompatible declaration of AreYouThere, first with dllexport, then second time with dllimport.
So you need a separate header only containing unmanaged code and managing the import/export problem.
Typically, you'd have something like:
#ifdef INSIDE_MY_DLL_IMPLEMENTATION // invent up some better name yourself...
#define DLL_IMPORT __declspec(dllexport)
#else
#define DLL_IMPORT __declspec(dllimport)
#endif
DLL_IMPORT void areYouThere();
In referencing project, you'd just include the header then, inside DLL code, you'd have instead:
#define INSIDE_MY_DLL_IMPLEMENTATION // must precede, of course...
#include "new_interface_file.h"
Generalising now: You can use this pattern for any DLL, managed or purely unmanaged alike. For the latter case, you could even consider different compilers (e. g. __attribute__((dllimport)) for GCC, although you might need some extra work as GCC attributes don't precede, but follow function declaration). Solely: different C++ implementations (compilers) most likely come with incompatible ABI, so you should fall back to a pure C interface if you plan multiple compiler compatibility:
#ifdef __cplusplus
extern "C"
{
#endif
// ...
#ifdef __cplusplus
}
#endif
I need to import a dll made in c# from c++
All the examples I found import a single function from a dll, but as far as I know, you cannot export a single function from c# without exporting the whole class (I'm a bit of a c# newbie though)
I am using node gyp to compile it (I'm building a node module for my web app using v8)
Here is my c# code:
using System;
using System.IO;
using System.Runtime.InteropServices;
[ComVisible(true)]
public class Hello
{
public static void Main()
{
Console.WriteLine("Hello World!");
string createText = "Hello World" + Environment.NewLine;
File.WriteAllText(".\\asd.txt", createText);
}
}
And this is my c++ header file:
#ifndef ASDLIB_H
#define ASDLIB_H
#define ASD_IMPORT __declspec(dllimport)
#define STDCALL __stdcall
class ASD_IMPORT Hello{
public:
STDCALL static void ASD_IMPORT Main();
};
#endif // ASDLIB_H
I normally do this kind of stuff by creating a static C++ CLR Wrapper Lib.
These are the steps I'm normally using (although I don't use it very often):
Here minimal example with using Visual Studio:
1. Create managed C# .NET library Project
Let name it HelloLibManaged
with one file Hello.cs and following content:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace HelloLibManaged
{
public class Hello
{
public void Print()
{
System.Console.WriteLine("Hello from Managed Lib");
}
}
}
Build this lib with x86 or x64 , just dont Any CPU
2. Create a new C++ CLR static lib project within same solution.
Let's name it HelloLibCpp
Add a reference to HelloLibManaged project via Project->Add Reference
Remove automatic created existing .h/.cpp files from Project, and create these 2 files:
HelloUnmanaged.h
#pragma once
namespace hello_managed {
class Hello
{
public:
void Print();
};
}
and
HelloUnmanaged.cpp:
#include "HelloUnmanaged.h"
namespace hello_managed
{
void Hello::Print()
{
HelloLibManaged::Hello^ hello = gcnew HelloLibManaged::Hello();
hello->Print();
}
}
Und Project Properties -> General specify static lib.
In the Build settings specify x86 / x64 - use the same build type as building Managed lib from Step 1.
Now you can build the dll and use it in your other unmanaged C++ projects.
For more advanced stuff, like return types and methods with parameters you have to do Type-Marshalling between managed/unmanaged code. There are many resources online with more information about Type-Conversion between managed/unmanaged code. Keyword: Marshaling.
In C#, how can I import all classes from one namespace into another namespace such that these classes are directly accessible from the second namespace?
I'm essentially attempting to rename a namespace in an externally visible manner.
Since code is worth a thousand words, given a DLL with the following namespace:
// Externally written DLL I have no control over.
namespace A
{
class ClassA {...}
}
I'd like to be able to create another DLL along the lines of:
// My DLL
namespace Wrapper
{
using A;
}
So that I can use it like:
// Final C# program.
using Wrapper;
var a = ClassA();
In python, I could accomplish what I want with import *:
# external.py
class ClassA:
...
# mymodule.py
from external import *
# final_program.py
import mymodule
a = mymodule.ClassA()
Disclaimer
I know this is a terrible idea, but I'm unfortunately being constrained by external requirements. The short version is that I have an external DLL that needs to interface with a proprietary system (EnScript, if you're curious). This proprietary system has restrictions on the naming of namespaces that the external DLL of course violates. Thus, I'm attempting to use the wrapper DLL to expose a namespace that is considered valid.
Related Questions
Talks about using in C# vs wildcard imports in java/python. Does not address issue of accessing from second namespace:
Import all subclasses like Java but in C#
C# equivalent to wildcard imports in Java
Namespaces in C# vs imports in Java and Python
Question about including classes in namespace. Issue was use of separate projects and so not applicable to this question:
How To Include Classes From Another Namespace In Assembly Instead of Writing Them Into A Separate DLL File?
You can't move a type to a different namespace (other than physically moving the code). The .NET type system uses the full namespace to uniquely identify the type.
But you can create an alias to mask the original namespace.
Let's say you have a class MyProject.Foo.Bar.Xyzzy.MyClass, and you are tired of typing MyProject.Foo.bar.Xyzzy. You can add a Using directive at the top of the code file like this:
Using DifferentNamespace = MyProject.Foo.Bar.Xyzzy;
Once you have done this, you can refer to the class with just
var c = new DifferentNamespace.MyClass();
You can even use this to include a different namespace in the current default namespace. This will compile:
namespace Example.Classes
{
class MyClass
{
}
}
namespace Example
{
using Example = Example.Classes;
class Test
{
static void Test1()
{
var c = new Example.MyClass(); //Not Example.Classes.MyClass
}
}
}
But unfortunately you have to leave the alias there; i.e., this won't compile:
namespace Example.Classes
{
class MyClass
{
}
}
namespace Example
{
using Example = Example.Classes;
class Test
{
static void Test1()
{
var c = new MyClass(); //Error
}
}
}
I am working on WP8 project that includes class library project as C# source code and Windows Runtime Component as C++ source code. Does anyone know whether or not it is possible to create such C# class library which would reference Windows Runtime Component? The ultimate result should be .NET assembly and .WIMND/.DLL runtime component that can be used for application. Currently I cannot build class library because it doesn't see Windows Runtime Component, even though I added it to the project.
More specific. I have, say, MyNs.MyClass.MyMethod() which is defined in C++ runtime component and used from C# class library. Currently I cannot compile C# due to missing method although I have windows runtime component project attached to the same solution.
Although I am butting in because this is not my area, I tried Googling for "c# call windows runtime component". There seem to be many hits/examples, e.g. the first one is https://msdn.microsoft.com/en-us/library/hh755833.aspx.
Does that not help you?
I solved this by adding reference to Windows runtime component manually into the C# class library .csproj file as follows
...
<ItemGroup>
<Reference Include="WindowsRuntimeComponent.winmd" />
</ItemGroup>
...
I managed to make a C++ WRL project and use a class in that project from a C# project by adding a reference in the normal way. The Wrl project (not C++/CX, which also works) was made using some WRL template that I found somewhere on the web. The wrl project required me to make a .idl to define the interface, and produced its .dll and .winmd. Here is some code for those who are battling with this type of thing:
The Wrl class:
#include "pch.h"
#include "WrlTestClass2_h.h"
#include <wrl.h>
using namespace Microsoft::WRL;
using namespace Windows::Foundation;
namespace ABI
{
namespace WrlTestClass2
{
class WinRTClass: public RuntimeClass<IWinRTClass>
{
InspectableClass(RuntimeClass_WrlTestClass2_WinRTClass, BaseTrust)
public:
WinRTClass()
{
}
// http://msdn.microsoft.com/en-us/library/jj155856.aspx
// Walkthrough: Creating a Basic Windows Runtime Component Using WRL
HRESULT __stdcall Add(_In_ int a, _In_ int b, _Out_ int* value)
{
if (value == nullptr)
{
return E_POINTER;
}
*value = a + b;
return S_OK;
}
};
ActivatableClass(WinRTClass);
}
}
The C# code that uses this class:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.VisualStudio.TestPlatform.UnitTestFramework;
namespace CSharpClientToWrl
{
[TestClass]
public class UnitTest1
{
[TestMethod]
public void TestMethod1()
{
WrlTestClass2.WinRTClass _winRtTestClass = new WrlTestClass2.WinRTClass();
int _answer = _winRtTestClass.Add(4, 6);
Assert.AreEqual(_answer, 10);
}
}
}
The .idl file of the wrl project:
import "inspectable.idl"; import "Windows.Foundation.idl";
#define COMPONENT_VERSION 1.0
namespace WrlTestClass2 {
interface IWinRTClass;
runtimeclass WinRTClass;
[uuid(0be9429f-2c7a-40e8-bb0a-85bcb1749367), version(COMPONENT_VERSION)]
interface IWinRTClass : IInspectable
{ // http://msdn.microsoft.com/en-us/library/jj155856.aspx // Walkthrough: Creating a Basic Windows Runtime Component Using WRL HRESULT Add([in] int a, [in] int b, [out, retval] int* value);
}
[version(COMPONENT_VERSION), activatable(COMPONENT_VERSION)]
runtimeclass WinRTClass
{
[default] interface IWinRTClass;
} }
I have a C# DLL file project (my_cs_dll.dll) which defines a static class with a static member function.
namespace Foo
{
public static class Bar
{
public static double GetNumber() { return 1.0; }
}
}
I also have a C++ DLL project which is using /clr.
#using <my_cs_dll.dll>
double get_number_from_cs() { return Foo::Bar::GetNumber(); }
I've added a reference to 'my_cs_dll.dll' in the C++ project Common Properties references section (copy local/copy dependencies are both True).
And I've also added the path to 'my_cs_dll.dll' in the C++ project Configuration Properties C/C++ General 'Resolve#using References' section.
Everything builds without error, however at runtime I keep getting a 'System.IO.FileNotFound' exception from the system claiming it can't find the my_cs_dll.dll assembly.
Both DLL files are definitely present in the same directory from which I'm running.
I have tried all sorts of variations on the settings mentioned above and read everything I could find on manged/unmanaged interop, but I can't seem to get my brain around what is wrong...
I'm using Visual Studio 2008 and .NET 3.5.
It sounds like your C# assembly is not being resolved at runtime. Is your C# dll in the same directory as (or a subdirectory of) your executable? It's been a while since I did this, but my recollection is that unless your assembly is installed in the GAC, it must be in the directory (or a subdirectory) where your executable is located, as opposed to the location of the dll that's using it. This has to do with the .NET security features.
If you are still having problems, you can try using resolving the assembly yourself. In your clr-enabled C++ project, try adding the following:
using namespace System;
using namespace System.Reflection;
void Resolve()
{
AppDomain::CurrentDomain->AssemblyResolve +=
gcnew ResolveEventHandler(OnAssemblyResolve);
}
Assembly ^OnAssemblyResolve(Object ^obj, ResolveEventArgs ^args)
{
#ifdef _DEBUG
String ^path = gcnew String(_T("<path to your debug directory>"));
#else
String ^path = gcnew String(_T("<path to your release directory>"));
#endif
array<String^>^ assemblies =
System::IO::Directory::GetFiles(path, _T("*.dll"));
for (long ii = 0; ii < assemblies->Length; ii++) {
AssemblyName ^name = AssemblyName::GetAssemblyName(assemblies[ii]);
if (AssemblyName::ReferenceMatchesDefinition(gcnew AssemblyName(args->Name), name)) {
return Assembly::Load(name);
}
}
return nullptr;
}
You may have to tweak the code a little bit to get it to compile in your project. In my case, I made the two functions static methods of a class in my clr-enabled project. Just make sure you call the Resolve() function early on in your code, i.e., before you try to call get_number_from_cs().
While using COM is an option, it is not necessary. You're on the right path with your current approach. If you want some hand-holding, take a look at this CodeProject example. It's the one I following to get my unmanaged application to use my managed assemblies.