here i am writing wrapper to call c++ function in c# project.Here i am not using Dllimport method. I am looking C++/CLR approach. using C++/CLR approach we can add Dll directly to the c# project.
In my C++/CLR i have one function like below.
int StartScan(std::list<SomeObject*> *DeviceList);
i want call this function from C#. what's the equivalent property to call from C#.
i have tried with LinkedList which is equivalent property for std::list, if we used P/Invoke Approach.
You can't. Since your question implies that you are using C++/CLR and that you have control over that code, you should write the public method C# is supposed to use to take a managed List<T> object as the parameter, and then copy the contents to the std::list<SomeObject*> object that your C++ code apparently actually needs.
You'll need a managed type for T, something that is equivalent to the SomeObject you're using in C++. You'll have to clone those objects from the managed type to your std:list as well.
If you aren't able to change the C++/CLI code, then you'd have to write a shim DLL to handle the conversion. P/invoke doesn't know how to do this automatically.
If you are able to use the STL/CLR library, as recommended in this comment, i.e. you can switch your std:: library usages to the cliext:: library, then it includes code to help with this. For example, you can create a cliext::list object, pass your managed List<T> to its constructor, and it will copy the contents of your managed list to the cliext::list object.
For example: How to: Convert from a .NET Collection to a STL/CLR Container
Related
I currently have a large C++ library that I need to incorporate into a C# project. I was successful in using DllImport to get access to some functions from my library, like this:
[DllImport("MyLib.dll")]
public static extern int SampleFunction(string param);
However, I can't seem to figure out how to make it work for functions that either have a parameter or return type that is not defined within the dll itself (i.e., the code in the dll imports it from another file), such as this example function that takes in a list:
[DllImport("MyLib.dll")]
public static extern std::vector<MyClass> MyFunction(string param);
For std library functions, I know I can get the dll and import that in, but what about other classes like MyClass in the above example? Do I need to create a managed wrapper class in C++ for each of these classes, or is there another way to do this?
std::vector<MyClass>, or indeed any unmanaged C++ class, cannot be used for interop to C#. Indeed, even if you wished to consume this function from another unmanaged C++ module you'd have to make sure that you were using the same compiler and dynamic runtime as the DLL which exported the function.
You'll need to find some other way to implement this functionality. There are lots of different ways to do that.
You could expose a p/invoke interface to the functionality. That would likely involve declaring a struct to represent the data of your class, and serializing to and from that struct.
You might consider a COM interface but it won't offer great advantages over p/invoke. You'd still need to serialize your class.
A C++/CLI wrapper would be yet another option. You'd wrap the unmanaged class with a managed C++/CLI class, and then consume that from the C#.
If you need a custom class from a native lib, you'll probably need to export a type library or use managed C++ to write a wrapper. What you're effectively trying to do is marshal a piece of memory from native to managed and now have to deal with how the data type is marshaled.
If at all possible, I would actually recommend trying to do away with the marshaling as when it works it's fine, but when it breaks, it can be rage inducing to debug.
Regardless, I'm actually not sure if anything in the STL can be marshaled. At the very least, I have never seen it done. More times, I've had to do a conversion like so: How can I marshall a vector<int> from a C++ dll to a C# application?
If you want to marshal an actual class, the standard way I've done it up until now is through a type library: Import TLB into C#
Or by linking a native lib into a managed C++ class and then referencing the managed C++ dll into the C# project as a shim.
Beyond that, if you can convert the class to strict C-style functions and pass a struct around, that could allow you to just use pinvoke, this is no different from simply exporting a bunch of helper functions except you can marshal a struct representation back and forth: Marshal C++ struct array into C#
I need to create the classes in C# and call that classes from javascript through C++CLI and Firebreath Framework .. create the complex hierarchy class structure and expose it from javacsript
The flow should be :
Javascript <-- C++(FireBreath)<-- C#
C#-->C++(Firebreath)-->Javascript
I have to create the generalized solution for this problem.
Then how should i implement this? If you have any solution,sort of information ,ways to solve this problem then please let me know..
Suppose my Class Library in C# which includes the classes like :
public class TestImage
{
}
public class DrawImage
{
public void ShowImage(TestImage testImage)
{
}
}
Here I need to call ShowImage(TestImage testImage) method from JavaScript page of Firebreath Framewaork.
I already created the wrapper but I dont have an idea to expose the class object as argument to the method like the above ShowImage () in tjhe JavaScript page of the Fireabreath Framework.
If you have any idea related to this please let me know.
When you say "generalized solution"... do you mean a tool or process that automates this?
I believe this is possible. Here's how I would do it:
I'm assuming you have gotten started with FireBreath and have some understanding of it. I'm glossing over countless problems you'll run into integrating all this within a FireBreath solution; that would take days! So this is just architectural advice. I'm sorry to omit so many details.
I would write a tool that dynamically loads your .NET assembly or assemblies, and uses reflection to traverse the 'complex hierarchy class structure'. This tool would generate two things: A C++/CLI wrapper for your .NET library, and a set of native C++ FireBreath classes that bind from Javascript to that C++/CLI wrapper.
The C++/CLI wrapper (see enter link description here) makes your .NET library callable from the native C++ of FireBreath.
Actually, here is a tool on CodePlex that claims to generate such a wrapper.
The Javascript adapter is a set of .cpp modules (probably one for each of your library/C++/CLI classes). Each of these is a C++ class derived from FB::JSAPIAuto, which allows these classes to be instantiated as Javascript objects. Within the constructor for each of these classes, the automated tool inserts code to create the object's Javascript API. Code that looks like this:
registerMethod("Start", make_method(this, &thisClass::Start));
registerMethod("Abort", make_method(this, &thisClass::Abort));
registerProperty("Size", make_property(this, &thisClass::get_Size,&thisClass::set_Size));
The automated tool must synthesize these methods of the class, like thisClass::Start and thisClass::set_Size. Their parameters and return types are the Javascript-compatible types supported by FireBreath - like int and double and bool, but also std::string, FB::VariantMap and FB::VariantList. In the body of each such method, the tool generates code to call the corresponding C++/CLI wrapper API, doing any necessary conversion between parameters and returns.
I suppose that each FB::JSAPIAuto-derived class inherits from, has as a member, or holds a pointer to, the C++/CLI class/object it represents.
As a FireBreath project, your .NET library is ultimately represented by a GUID - this is how Javascript finds its way into your library, by creating a root object from that GUID. It then calls methods or reads properties of that object to get other objects, and so on to access your entire library API.
I suppose there will be some issues mapping between Javascript and C#. You will have to study the Javascript parameter and return types supported by FireBreath, and limit your C# API accordingly. Probably key is figuring out how Javascript objects and arrays are represented as they cross the C++/CLI layer.
I've just achieved something like this using COM. I exposed the C# library as a COM object, then wrote a couple of wrapper functions which called this library in FireBreath. (I was lucky thought I had a very simple API).
I have to send a list from C# to C++.The C# list is List<string>MyList and the C++ code accepts it as list<wstring>cppList.How to use marshalas for this.
Thanks
It is always wiser not to use complex type marshaling between native code and managed code.
In case of List, these type totally differ from each other as they have different memory layout for each item.
So the best way is to write a utility function in a native dll that accepts array of string(char*) and manually build your native List and ultimately call the desired method. It is easy for your to create wrapper of that utility function.
C# cannot P/Invoke complex C++ types. You will have to use C++/CLI, they might have a method for marshalling it across. Else, you will have to marshal each string across individually.
strings in C# are wstrings (2 byte unicode strings), so if what you say is true, then no special conversions are necessary.
I want to import an unmanaged C++ DLL and call a function that takes stringstream as a parameter. In C#, there is no stringstream class, so can anyone tell me how to call such a function from a C# program?
You should not expose templated objects via a DLL, period.
Templated objects (e.g. almost everything in std::) become inlined. So in this way, your DLL gets its own private copy of the implementation. The module calling your DLL will also get its own private implementation of stringstream. Passing between them means you are inadvertently weaving two unrelated implementations together. For many projects, if you are using the exact same build settings, it's probably no problem.
But even if you use the same compiler, and mix a release DLL with a debug EXE, you will find stack / heap corruption and other harder-to-find problems.
And that's only using your DLL from another unmanaged C++ exe/dll. Crossing then the lines to .NET is even more of a problem.
The solution is to change your DLL's interface to something that plays friendly across DLL bounds. Either COM (you could use IStream for example), or just a C-style interface like the winapi.
If you can modify the C++ dll, export a plain string version. Otherwise you have to build a managed C++ wrapper project, import the other C++ dll, export it as a managed function, and call that from your C# code. C++ interop really sucks.
I'm afraid that you're going to have to create your own StringStream class in C# in order to be able to consume the functions exported from that DLL. As you mentioned, the .NET Framework doesn't provide any similar class out of the box.
The easiest way is probably to wrap the StringBuilder class provided by the .NET Framework such that it can function as a stream. See this blog post for a further explanation and some sample code.
A similar question was also answered in MSDN Magazine: http://msdn.microsoft.com/en-us/magazine/cc163768.aspx. You might find some of the hints and/or sample code given there useful.
You are trying to bind native C++ code to managed code in C#. Best way of doing that in general is to introduce middle layer in managed C++ that will provide interface to calls from C#.
Create an Wrapper dll in c, or c++ that exposes an friendly call to that function. It's the better way.
for example an
BOOL getString(TCHAR * myreturnString, DWORD *size);
I am importing the CreateICeeFileGen() function from the unmanaged DLL mscorpe.dll in a C# application, in order to generate a PE file. This function returns a pointer to an C++ object defined here, is there any way I can access fields from this class via C# or do I need to write an unmanaged wrapper DLL?
The code I'm using currently is as follows:-
[DllImport(#"C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\mscorpe.dll", EntryPoint = "CreateICeeFileGen")]
static extern void CreateICeeFileGen(out IntPtr iceeFileGenPointer);
...
IntPtr filePtr;
CreateICeeFileGen(out filePtr);
N.B.: I know you can do similar things with .net libraries but I need to use unmanaged libraries for my purposes.
You need a wrapper library to be able to use the class from C#.
The best bet would be to create the wrapper using C++/CLI, which can directly call the unmanaged function and expose the details with a managed class. This will eliminate the need to use P/Invoke for anything.
(Well, technically if you know the class layout you could mess around with pointer arithmetic to access the fields, but this would be very fragile and messy, and trying to call virtual functions in this way would be extremely ugly).
It looks like COM class/interface. Can you not just use COM instead?