I have a class decalred inside managed c++ dll as
public class IPHelper
{
public:
static void CheckIP(LPWSTR pSocketName);
static void DebugMessage(const wchar_t *str, ...);
private:
static DWORD GetIPInformation(PSOCKET_RECORD &pInfo);
};
I compiled it successfully and add it as reference to my c# project.
I am able to use the namespace, however the class seems empty and I'm unable to call the functions inside it.
Any ideas?
That class is not managed, it is native. You need to call it a public ref class if you want to use it from managed code.
You're going to need to invoke it using the P/Invoke method. See this reference for more information.
As others have noted, that's a native C++ class. Assuming your project is CLR enabled, then you can easily write a simple C++ / CLI wrapper around it, which will allow you to use it in a managed context.
This is a quick overview of C++ / CLI which should get you started in the right direction.
That class seems to be a hybrid. You specified public class IPHelper, which is halfway what you want. You should specify it as public ref class IPHelper. However even so, it will still not interface well with managed classes, because of the parameter types it receives. For instance a wchar_t is not the same as a System::String^ (managed C++ way to declare strings). Similarly a LPWSTR is also not the same as a System::String^. As a side note, it would be best for you to write some utility methods to convert between .NET System::Strings and wchar_t and other native strings that you will most likely need. This is an excellent article on MSDN on how to convert between all the various string types.
Now I don't know if you want to expose this class directly to C#, or have this class in turn wrapped by a better managed wrapper than what you have here. But anyway you do it, the Managed C++ class's methods have to take .NET types in order to be directly used in C# code.
Related
I have a vendor's DLL that is meant to be called from C++, but I need to call it from C#.
Using an app called PE Explorer I can see the list of exported methods in the DLL (call it Protocol.dll for now) and even get an 'Undecorated C++ Function' signature like this:
public: unsigned int __thiscall Myco::Protocol::tMultiThingClient::GetThings(char (* const)[16],unsigned int)
How do I use something like that in C#? I know I use DllImport, I just don't know how to go from the signature above to a proper DllImport signature.
Total WAG:
[DllImport("Protocol.dll", EntryPoint="GetThings")]
public static extern void GetThings(ref string[], uint);
Is that even close? Is there a reference somewhere that translates between C++ declarations like char (* const)[16] and their C# equivalents?
You need to create a seperate project containing mixed assembly using C++ CLI. For this, you need to enable the CLR compiler switch in your project properties. Since, the project allows mixed assembly, you can call the C++ function, and also create a C# interface for your main program to call.
So, your main program will call the interface you implement inside your C++ CLI project, which will in turn call the C++ funtion inside the DLL.
Please beware of Marshalling and Thunking while you do this, if it applies to your system considerations.
Let's assume I have an unmanaged class Test:
class Test
{
public:
int SomeMethod(int a, bool b);
};
To create a new instance of Test, I'd:
Test *test = new Test();
My goal is to embed Mono so that managed code could call unmanaged methods (like Test::SomeMethod) in a specific object. I represent that object by passing a pointer of that object to the managed method, like that:
void *args[1];
args[0] = &test;
mono_runtime_invoke(init, NULL, args, NULL);
Here is how the managed method that is being invoked looks like:
public static void Init(IntPtr test)
{
}
From here, how can I call Test.SomeMethod?
I thought about using emitting the CALLI instruction, using System.Reflection.Emit, but how can I refer to the object that the pointer test (the first parameter of Init) is referring to?
I do not want to use DllImport.
You might be interested in CXXI. It creates a managed assembly based on your C++ headers and allows you to work with C++ objects as if they were normal managed objects.
As far as I understand it, it's not finished yet and works only with C++ code compiled by GCC.
Can't be done (Or at least shouldn't be done).
You're trying to directly mix two completely different execution environments - the reason why DLLImport exists is to allow the compiler to solve this problem.
In .NET, you can create mixed-mode applications (C++/CLI) which allow managed code and unmanaged code to co-exist in the same binary (and call each other), but since you're talking about mono, I'm assuming that option is out.
Managed environments like .NET have strict type rules, garbage collection and other features that simply don't work with unmanaged code and data.
You can use an internal call, if you don't want to use DllImport.
See https://github.com/mono/mono/blob/master/samples/embed/teste.c the mono_add_internal_call() invocation and the C# code in the test.cs file.
This works mostly like DllImport, except there is no marshalling done for you (a string object in C# code will appear as a MonoString* in the C code, not as a char*, for example).
In any case, note that both the function you could access with DllImport and the function pointer registered with mono_add_internal_call() must be C functions, not C++ member methods.
I am attempting to write a DLL using the C# .NET Framework 2.0. Everything compiles okay, but when I try to access the DLL from my application, it fails when attempting to get the procedure address. So, I oped the DLL in Dependency Walker, and all of my public functions are missing!
My DLL, so far, is fairly straightforward:
namespace MyDll_Namespace
{
public class MyDllClass
{
public static int Func1( /* params */ ) { /* ... */ }
public static int Func2( /* params */ ) { /* ... */ }
public static int Func3( /* params */ ) { /* ... */ }
public static int Func4( /* params */ ) { /* ... */ }
}
}
There's not much else, just a few constants and delegates defined inside the class, as well as outside the class in the namespace. Any thoughts or suggestions would be much appreciated. Thanks.
Dependency walker is for win32 DLLs (which is native code), not .NET assemblies (which is managed code). It won't find methods in an arbitrary class (even if they are static). If you need to call managed code from native code, there are ways of doing that, but it's not pretty.
If you want to use your dll from managed code, it's a lot easier. Check out System.Assembly and Activator.
An example of this:
var assembly = Assembly.LoadFile(#"\path\to\your.dll");
var mydllclass_type = assembly.GetType("MyDllClass");
var instance = Activator.CreateInstance(mydllclass_type);
The instance will be an object. To call the methods, you need to use reflection, because the interface is not known at compile-time.
If you are creating a plugin system, the best way is to have a common interface or abstract base for all plugins, and have that referenced by your program. Those third parties who implement a plugin, will also reference this contract. In this case, the last line changes a bit:
var instance = (IMyDllClass)Activator.CreateInstance(mydllclass_type);
Now you can use the methods like in a regularly constructed object.
Part of the problem here is that dependency walker is a tool for native applications. It doesn't understand managed code and hence won't display any of the managed types + methods that you've defined.
I'm confused by this line in your question
when I try to access the DLL from my application, it fails when attempting to get the procedure address
This sounds a bit like an error I would see in a native application, not a managed one. Are you trying to access the C# code from a native application? If so this can only be done via COM magic and not via direct calling. Can you explain in more detail what is going on here?
Try .net Reflector to see exactly what's inside your built DLL (in order to make sure everything is the way it is supposed to).
Also make sure you're in release mode while building your DLL before referencing it... I don't know if it's going to change anything, but it worths the try =)
You need to add a reference to your dll and the runtime will automatically allow you to call your function. Here is a little tutorial on writing a .net class library.
I decided to write my DLLs in C++. However, here is a bunch of useful information I found for using managed code from unmanaged code:
Is it possible to use a DLL created using C# in an unmanaged VC++ application?
How do I call C++/CLI (.NET) DLLs from standard, unmanaged non-.NET applications?
Using managed code in an unmanaged application
Using Managed Components from Unmanaged Code
An Overview of Managed/Unmanaged Code Interoperability
Unmanaged Exports
Calling Managed .NET C# COM Objects from Unmanaged C++ Code
All-In-One Code Framework
CLR Hosting APIs
How To: Migrate to /clr
How to call a managed DLL from native Visual C++ code in Visual Studio.NET or in Visual Studio 2005
i need to bind C++ dll to my C# WinCE program. (scanner dll)
how i can do it ?
thank's in advance
You need to use Interop to call into unmanaged code.
using System.Runtime.InteropServices; // DllImport
public class Win32 {
[DllImport("User32.Dll")]
public static extern void SetWindowText(int h, String s);
}
Here is an article that discusses the topic in detail (also where the code is sourced from).
http://msdn.microsoft.com/en-us/magazine/cc301501.aspx
An alternative to InterOp is to write a C++ DLL using CLR extensions which acts as a wrapper to the traditional C++ DLL. This gives you a chance to handle unusual types, e.g. custom structures or classes, if Marshaling isn't going to work. (According to MSDN you can extend the Marshaling support (http://msdn.microsoft.com/en-us/library/bb531313.aspx) but I haven't tried this personally, and depending on what you're doing it might be a lot of work).
For example if you want to access a DLL which exports a class, you can have a wrapper DLL which owns an instance of the C++ class and defines a .NET class which maps onto the C++ class. For example, here's a snippet from a C++/CLR DLL which we use to make one of our old C++ DLLs available in .NET:
// This is the constructor for the CLR (managed) object
FileInf::FileInf()
{
// Create the C++ (unmanaged) object
m_pFileInf = gcnew DILib::FileInf();
}
// This is a managed interface which replicates the old
// unmanaged functionality
bool FileInf::IsDirectory()
{
return m_pFileInf->IsDirectory();
}
I'd say if InterOp works then stick with it, but I'm not sure if it's the best way to solve every C++ / .NET interfacing problem, and this is an alternative.
Suppose I am writing an application in C++ and C#. I want to write the low level parts in C++ and write the high level logic in C#. How can I load a .NET assembly from my C++ program and start calling methods and accessing the properties of my C# classes?
You should really look into C++/CLI. It makes tasks like this nearly trivial.
Otherwise, you'll have to generate COM wrappers around the C# code and have your C++ app call the COM wrappers.
[Guid("123565C4-C5FA-4512-A560-1D47F9FDFA20")]
public interface IConfig
{
[DispId(1)]
string Destination{ get; }
[DispId(2)]
void Unserialize();
[DispId(3)]
void Serialize();
}
[ComVisible(true)]
[Guid("12AC8095-BD27-4de8-A30B-991940666927")]
[ClassInterface(ClassInterfaceType.None)]
public sealed class Config : IConfig
{
public Config()
{
}
public string Destination
{
get { return ""; }
}
public void Serialize()
{
}
public void Unserialize()
{
}
}
After that, you need to regasm your assembly. Regasm will add the necessary registry entries to allow your .NET component to be see as a COM Component. After, you can call your .NET Component in C++ in the same way as any other COM component.
I would definitely investigate C++/CLI for this and avoid COM and all the registration hassles that tends to produce.
What is the motivation for using C++? If it is simply style then you might find you can write everything in C++/CLI. If it is performance then calling back and forth between managed C++ and unmanaged code is relatively straight forward. But it is never going to be transparent. You can't pass a managed pointer to unmanaged code first without pinning it so that the garbage collector won't move it, and of course unmanaged code won't know about your managed types. But managed (C++) code can know about your unmanaged types.
One other thing to note is that C++/CLI assemblies that include unmanaged code will be architecture specific. You will need separates builds for x86 and x64 (and IA64).
If you can have both managed and unmanaged code in your process, you can create a C++ class with virtual functions. Implement the class with mixed mode C++/CLI. Inject the implementation to your C++ code, so that the (high-level) implementation can be called from your (low-level) C++ code.
You can wrap the .NET component in a COM component - which is quite easy with the .NET tools - and call it via COM.
If the low level parts in in C++ then typically you call that from the C# code passing in the values that are needed. This should work in the standard way that you're probably accustomed to. You'll need to read up on marshalling for example.
You could look at this blog to get some concrete details.
Create your .NET assembly as normal, but be sure to mark the class with the ClassInterface(ClassInterfaceType.AutoDual) and be sure an assembly info SetAssemblyAtribute to ComVisible( true ).
Then, create the COM wrapper with REGASM:
regasm mydll.dll /tlb:mydll.tbl /codebase f:_code\ClassLibraryForCom
be sure to use the /codebase directive -- it is necessary if you aren't going to give the assembly a strong name.
rp
Since C# can import C++ standard exports, it might be easier to load up your C++ dll inside of a C# application instead of using COM from C++.
See documentation for System.Runtime.InteropServices.DllImport.
Also, here is a complete list of the types of Interop that you can do between managed and unmanaged code:
http://blogs.msdn.com/deeptanshuv/archive/2005/06/26/432870.aspx
In a nutshell:
(a) Using COM-Interop
(b) Using imports/pinvoke (explicit method calls)
(c) IJW and MC++ apps : MC++ & IJW apps can freely call back and forth to each other.
(d) Hosting. This is rare, but the CLR can be hosted by an unmanaged app which means that the runtime invokes a bunch of hosting callbacks.
I found this link to embedding Mono:
http://www.mono-project.com/Embedding_Mono
It provides what seems to be a pretty straightforward interface for interacting with assemblies. This could be an attractive option, especially if you want to be cross-platform