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Is is possible to export functions from a C# DLL like in VS C++?
(4 answers)
Closed 6 years ago.
I have a .net assembly written in C#, and I'm looking to export a native C function from the assembly.
I have an application which will perform a 'LoadLibrary()' on any DLL's found in a 'plugin' folder. After loading the DLL, the application performs a 'GetProcAddress' looking for a function named 'Register'. The application expects this function to follow the C calling convention.
How can I export a function named 'Register' from my .net assembly, so I can successfully hookup with the plugin system for this application?
Thanks,
Andrew
Have a look at Unmanaged Exports.
Write a .Net library in Managed C++ and there you can export a "Native" method/function.
Sadly Microsoft does not support this feature, and you have to change the msil after the build to expose those methods.
It is possible as one guy has shown a reasonable solution
on codeproject or here,
but it requires a post build step and you are on your own after that.
I don't know if this hack will work on .net 4.0 or later though.
Hopefully Microsoft will listen to us and support this simple feature in C# since the CLR support is already there.
What you want is a Reverse P/Invoke. You can't actually embed a C function in a C# dll, if by that you mean a function actually implemented in C, but by following the tutorials given on the linked page you can create a DLL export that's callable by unmanaged C/C++ code.
Related
In VS C/C++ you could use extern "C" __declspec(dllexport) -function declaration-.
How do I accomplish this in a C# dll? Is there C# code equivalent to the above code?
Edit: More info
I am trying to create an add in for Notepad++ and I want to use C#, but the common way I've seen so far is to use legacy C++ code with the above call to export a few of the functions that Notepad++ expects to import and call. There is an example app using C#, but this still requires a loader DLL, which I assume from the comments/answers below is the only way for C#.
Unmanaged Exports =>
https://sites.google.com/site/robertgiesecke/Home/uploads/unmanagedexports
DLLExport => https://github.com/3F/DllExport
How does it work?
Create a new classlibrary or proceed with an existing one.
Then add the UnmanagedExports Nuget package.
This is pretty much all setup that is required.
Now you can write any kind of static method, decorate it with [DllExport] and use it from native code.
It works just like DllImport, so you can customize the marshalling of parameters/result with MarshalAsAttribute.
During compilation, my task will modify the IL to add the required exports...
I've seen people do this before, but it required ildasm, adding the MSIL .export directive, and then reassembling. A program named dll_tool can do these steps for you.
If you want to build a mixed-mode DLL with both native and managed exports, you should be using C++/CLI, which is specially designed for this purpose.
Yes, it is possible to export functions from a C# dll in much the same way that C++ does it! You need a little help from an add-in Unmanaged Exports (DllExport for .Net) that facilitates this process, or from a similar method such as Exporting functions in C#/VB.NET to native code.
Please see Code to Export C# DLL to Metatrader Build 600+ for a working example using Robert Giesecke's C# Project Template for Unmanaged Exports to export a C# dll to a legacy application (Metatrader) that has a great deal of similarity to C++.
Additionally, you might find Native and .NET Interopability interesting though it is mostly geared toward accessing native code from within .NET rather than the other way around.
No, you cannot do that in the same sense as you do in C and C++.
But you can create COM API to achieve that which then you can use in C and C++ code.
See these articles
C# Classes as COM Objects
Calling Managed .NET C# COM Objects from Unmanaged C++ Code
COM Interop Part 1: C# Client Tutorial
This question already has answers here:
Call C# dll from Delphi
(3 answers)
Closed 7 years ago.
As my first time as a student employee programming I have to create a DLL in C#.NET which is callable from Delphi.
I've read about this being not so easy due to Delphi being native code and .NET being managed.
I've also read about 'Unmanaged Exports' from Robert Giesecke. Could this be the solution?
Since I do not have Delphi on my machine (Delphi isn't free), I can't test this out for myself.
Also, will I have problems with my datatypes when I implement the Unmanaged Exports?
Last but not least, is there a language I could use that would have the same problem as Delphi for loading the DLL? It'd be nice for me to be able to test.
UnmanagedExports is one option. It certainly works very well. Other options include:
Exposing the functionality using COM.
Exposing the functionality via a C++/CLI mixed mode assembly.
Hosting the CLR from your Delphi code.
The final option is not very tractable. Don't attempt to do that.
You'll almost certainly encounter problems with interop data types unless you are already an expert in the field.
You can certainly test this out with FreePascal. Very likely you can write code in FreePascal that consumes your .net assembly and later use the exact same code in Delphi. Even if you have to change it somewhat, the lessons you will learn will be exactly the same.
You can make your .Net DLL as Com visible. Check this link.
Delphi can load Com objects without problems. This in theory, I don't have specific code samples, but you can try with different tutorials, they practically explains the same.
I don't know about the data types, but COM always tries to cast to a base type (double, float to decimal, number to integer, and complex objects to dynamic objects).
You can use the .Net Runtime Library for Delphi in http://dotnetruntimelibraryfordelphi.sourceforge.net/
The runtime library allows you to host and access .net library types.
This question already has answers here:
C# library to native C++ application
(3 answers)
Closed 3 years ago.
What is the best solution to access c# code via native code (C++)?
I have C# code which I want to call from native project, so I'm considering writing a COM wrapper but I wonder whether there is a better option (framework/design pattern/architecture etc.) available in .NET?
COM interop is without a doubt the best bet. It's a known, supported framework for achieving exactly what you want to achieve.
There is another alternative however - it is possible to edit the IL code inside a compiled .NET assembly to flag methods within the assembly as native exports. A detailed breakdown of the changes can be found in this CodeProject article.
Robert Giesecke has created Unmanaged Exports to simplify this process using simple method attributes. A NuGet package can be found here.
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Wrapping C++ for use in C#
(3 answers)
Closed 9 years ago.
I have a C++ project which consists of some headers, cpps, some lib files and DLL files.
I want to wrap these files in order to use them on a C# project.
I wanted to make one DLL which will contain the all C++ project and then to wrap it with C# class so I would be able to work with it.
So my questions are (Working with Visual Studio 2010):
How do I make the final DLL file.
a. I know how to link the lib files to the project, but how do i link the DLLs?
b. What do I need to add to my headers in order that the functions declared in them (which are implemented in the lib files) will be imported to the DLL. (What is __declspec)?
After building the final DLL file, how do I create a C# project which use this DLL file?
Thanks in advance
This is called (COM) InterOp. Fortunately one of the major design goals of the original .NET Framework was to facilitate easy interoperability between managed and unmanaged code. Broadly speaking there are three different kinds of interoperability that one may wish to achieve when dealing with managed code.
Making calls into COM components from managed code
Making calls into native DLLs from managed code. This known as platform invocation or colloquially, PInvoke. (This is what you want)
Allowing COM components to call managed code by wrapping the managed code with a runtime callable wrapper (RCW). This can be used as a strategy for the piecemeal replacement of legacy code on a planned basis.
The process by which data is moved from the managed to unmanaged realm is known as marshalling. This is the name by which data and its associated types are serialised across some boundary or other. To support this process there are a collection of classes that exist under the System.Runtime.InterOp namespace.
Broadly speaking the process is essentially as follows:
Determine function names (I use Dependency Walker)
Determine function signatures (Look it up on MSDN if it's a MSFT one)
Determine data types and structures required by code
Write managed code to call into the native code that satisfies the criteria determined above
Test the wrapper code that's after being written to ensure that it produces the expected results (this can often be the most tedious part)
You are looking for C++/CLI. With this hybrid you can write a dll that can contain any amount of normal C++ code and it can contain managed classes that can use .NET types (like System.String) for it's interface and internally handle your normal C++ types. That dll will be usable from C# like any other .NET dll. From the calling programs perspective will look as if you had written it in C#.
Normally answers should contain practical examples, but C++/CLI is a large field to cover, you could write books just describing your scenario. You can find a good tutorial here and a good Overview here.
This question already has answers here:
Using C++ Class DLL in C# Application
(5 answers)
Closed 8 years ago.
All in the title really. I have a library, written in c++ and compiled into a dll. I would like to use this functionality in a c# program. Is it possible to use the classes/functions from the library straight from c#, would I need to write some wrapper code to use it in a managed environment? Can they be used in an unsafe context? Sorry if this is a silly question - I'm a c++ programmer trying to move over to c#.
p.s. the library is from a third party, so I cannot port it direct to c# even if I had the time.
It depends on how the C++ dll exports it's functionality.
If it's through C++ classes, then your best bet is to build a wrapper in C++/CLI that will consume the C++ classes and expose .NET classes to interact with them.
If it's through "classic" C-style functions, then you can use p-invoke to call the functions directly. It would be similar to the ways system DLLs like System32 and User32 are accessed.
Yes it's possible!
First add the reference to System.Runtime.InteropServices:
using System.Runtime.InteropServices;
After you have to import the function on the external Dll:
[DllImport("ExternalDLL.dll", EntryPoint = "FunctionNameOnExtDll")]
public static extern CSharpDataType FunctionNameOnExtDll(ParameterDataType ParameterName);
And finally use it!!
FunctionNameOnExtDll(Parameter);
Yes it is possible, just knowing the signature of the functions you want to call and use System.Runtime.InteropServices facilities.
To help, use this tool PInvoke Interop Assistant that can help define data structures to be passed in calls.