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load C# dll in c++/cli and create a dll that works in unmanaged language

I have written a selenium script in C# and now I want to expose all functions and use them all in c++ code. My point is to deliver a dll to sb who wants to use this dll in pascal (delphi). The C# code is a complete code and all I want to do is to make a bridge between my C# and pascal.
I found out that pascal is an unmanaged language so C# code, which is a managed one, can not be consumed in pascal. For that reason, I started to write a c++ dll that uses my C# dll and makes a bridge between my C# and pascal code.
I've read all available topics on stackoverflow and these are what I've found useful:
expose my functions using COM
using c++/cli to communicate with my C# dll.
I started with the first one. I was able to create COM visible dll and use that in my c++ native code but I had problems with data types. I found it hard and moved on to the second option. But I'm not sure if I can wrap all my functions like that and let unmanaged languages use them.
a sample of my c# code:
namespace MainEngine
{
public static class StartMainEngine
{
public static void test_pascal(out string _result)
{
_result = "Hello World!";
}
}
}
my c++/cli code(I have referenced to my dll and visual studio shows me all functions inside my dll. So, It's not a dll import issue):
#using<ManagedLibrary.dll>
using namespace MainEngine;
char* r;
StartMainEngine::test_pascal(r);
Please guide me through this and let me know if I'm doing this in the correct way to be able to consume this dll in pascal.

It's possible using COM, CLR or IPC
Full answer you can find in this topic here

Passing Structure to C#

I am writing code to parse a complicated string in C++ and create a tree from it. I would like to use C# in Visual Studio 2017 to call a native c++ method that returns a vector of nodes.
A Node looks like:
class node
{
public:
std::vector<node> subnodes;
std::string name;
};
and the c++ function might look like:
class noderizer
{
public:
node getNodes(std::string str);
};
what is the most efficient (coding time with secondary consideration for speed) way to call the noderizer::getNodes(...) member and create a equivalent class for c#?
I am assuming that the best route is to create a duplicate class definition in c# and then copy marshal the native std::strings into managed Strings"
public class node
{
public string name = string.Empty;
List<node> integers = new List<node>();
}
It's not clear if this article contains the latest information for c++ interop, but a related article on wrapping c++ native classes for use in c# indicates that I could most likely just wrap noderizer native c++ as noderizer * m_Impl; and then call the getNodes member and copy over each parameter. Is this the correct methodology?

You could use pInvoke as per your first referenced article, but the objects you are returning seem quite complicated. I think you will have a heck of a time with data marshalling if you're not already well versed (and even then). pInvoke is great for simple calls to C libraries where data marshalling is basic, but it gets very complicated very fast. This is not good for your situation.
The second article is closer to where you want to look. That being said, you have to consider whether you want to be wrapping a managed class or just calling a function that takes a string and returns your tree in managed format (i.e. it makes a copy rather than wrap unmanaged data). By your post it seems like you just need the latter.
Your best option is to use C++/CLI. Check out this tutorial. I am confident that taking this approach will make light work of your task. I won't attempt to explain the subject as the article above does a very good job. In essence, you will be able write functions with both managed and unmanaged data types, where all the data marshalling is built into the environment. A simple cast will marshal the data for you behind the scenes. As a big bonus, debugging is great as you can step from C# to C++/CLI to C++ code and back.
In the article above, the author does describe how to wrap an unmanaged class, which you can well do, but your problem will still be with data conversion.
I would approach your problem in 4 steps:
Write a static function getNodes() in C++/CLI that you can call from C# as any regular static method, passing a string as an argument. The article above will help you with that. Also See Here when creating the C++/CLI project.
getNodes() will use your C++ code to create a tree in its unmanaged form.
Use getNodes() to convert the tree from unmanaged to managed form.
Return the result to the caller in C#.
your declaration will look something like this, where the Node is your managed calss, ref keyword signifies that the class is managed, and ^ is the managed version of *.
public ref class noderizer
{
public:
static Node^ getNodes(String ^mStr);
};
Here getNodes() calls your C++ function and does the data conversion. I don't think it will take you long to figure it out.
Once you get a hang of the syntax, I think you will find it quite intuitive to use if you are already familiar with C# and C++.
As for performance, unless you're making thousands of consecutive calls or need critical real time data, it should not be an issue. One thing I would say though, if you're concerned with performance, you should write the pure C++ code in a separate purely unmanaged dll. I can't find the article for the life of me, but I remember looking at some benchmarks of executing purely unmanaged long running code block that was compiled inside the C++/CLI dll vs calling the exact same code that was compiled inside its own purely unmanaged dll. If I recall correctly, the separate dll was something like 3x faster.

Passing Object as parameter in c /CLI Wrapper Function to be exported to native Win32 dll

I've been working recently in COM interop thing.Read some Good books about it C++/CLI in Action By Nishant Shivakumar. I also went through this link by Srinivas wherein he has explained beautifully how to Consume C# libraryin native C++ using C++/CLI.I downloaded the code present at the bottom of the page..Read it..And loved it.My application is loosely based on it. I have a question though in that example(which you can download it there).
In C# Library "Worker.cs",If I have a method in the Worker class with a signature like this::
public void GetStudent(ManagedStudent student,int ){....}
FYI:: I need the object parameter because I would be accessing a method from that class in the Worker Class.
In C++/CLI wrapper project, NativeInterface.h, I wanted to export a method which gets this managed object as a parameter unlike the example.
__declspec dllexport void GetStudent(ManagedStudent^ obj)
What is the equivalent of an object in C++/CLI?
And later I want to access this method by importing this method by passing an object in my native Win32 Application/DLL.
I am including the "NativeInterface.h" file in my native dll/App . But an error comes while building the dll/App..managed targeted code requires \clr option.
FYI::
1. My WIN32 dll/app is being compiled with no \clr support and my wrapper with \clr support
2. I believe the error comes because of the handle used as a parameter? I want to access UnmanagedStudent(Object obj) in native app/dll;
Is that possible

It's possible, but you can't pass a .NET object to a native DLL, which is a native C++ code...
The equivalent of an .NET object in native C++ is C++ object... but this is like asking a C# to understand Native or PHP, or....
So, there are several approaches.
Don't use C++ managed wrapper. Instead using Marsahling and C# interoperability directly call into native C++, in 1 of 2 ways:
Pass the object fields as a long list of parameters to the C++ and re-construct the object inside native C++. A bit "not nice" approach but very efficient and easy to debug.
You can also pass the object as a class pointer to the C++ native directly, you need first to create the right marshaling in C#. See here:
http://msdn.microsoft.com/en-us/library/system.runtime.interopservices.marshal(v=vs.110).aspx
Use C++ Interop (which you are doing...). You need to compile with Mixed mode! See this nice example:
http://social.msdn.microsoft.com/Forums/en-US/vclanguage/thread/f2de75c5-50a6-41ac-9ddf-694a8c0ce75b/
BUT... you need to understand the basics and know how to compile it:
http://msdn.microsoft.com/en-us/library/x0w2664k.aspx
Interoperability is a complex issue... and I try to write a short answer, please revert to me for further clarifications....

C source code to DLL for use in a C# application

I have a C source code written in VC++6.0 and I need that code to be used in a C# application which I am coding.
I have done few things to make that happen, I have run that C source file in release mode and have generated the intermediate.manifest file and the other files there, can I use any of these file to make my problem solved.

What you want to do is import the dll like this:
[DllImport("user32.dll")]//This is where you identify your dll...
public static extern int MessageBoxA( //This would be an object from your dll
int h, string m, string c, int type);
public static int Main()
{
return MessageBoxA(0, "Hello World!", "My Message Box", 0);
}
The keywords that you need to search on to learn about this are "running unmanaged code" and "PInvoke".

Another alternative is to wrap the C code in managed C++. Microsoft calls it C++/CLI. Anyways, you then compile an 'assembly' from that wrapper. An assembly is just a DLL that contains managed code. Then you can 'reference' (the managed equivalent of linking) that 'wrapper' from a fully managed C# application.
So the dependency could look like this:
C -> Managed C++ -> C#

If you are comfortable enough wrapping up c code in c++ you could easily make a dll by following this microsoft guide. It details how to go about creating a dll in C++. If you need a more in-depth explanation though feel free to get back to me, and I will try and knock up a quick how-to.
Also let me know if you use a different IDE or environment and I can taylor the answer to suit your needs more precisely.
Might be later on today though as am pressed for time at the moment.

talking to C from C#

I have a legacy code implemented in C (not C++). I would like to be able to call a few methods in this C code from my C# code (on Windows). What would be the best approach to interface between the two language? Please note that the method in C is not stateless. We need to call two methods:
initialization() => this will initialize the data structure and load data from files into memory. This method will be called once.
ComputeSomething(parameters) => there will be several calls from C# to this method.
Note: These two methods actually call several other methods but these are only the two methods that we would like to expose to C# (the code is quite complicated, that's why we do not want to port to C#)
I have been able to import the c code into visual studio and able to compile the code successfully. I know that we can probably implement the C code as windows service but I am looking for a solution that allow us to call C method from C# directly. Any pointers is highly appreciated! (is COM interop related to what I am looking to do?)

Sounds like you can use P/Invoke for this. Check out this site for tips:
http://www.pinvoke.net/
Also, try searching SO for advice on P/Invoke and Google for
c# pinvoke calling c code
I don't have any technical examples at hand, but I have written some .NET code which called Win32 API's via P/Invoke. The tricky part is getting the method signatures correct when passing parameters. This might help you out there.

Recent version of Visual Studio allow you to write C++ code that can call unsafe functions but still interface with CLR managed code. They call this "Implicit PInvoke," or "C++/CLR." Check out the MSDN article "Using C++ Interop" to learn more.
Managed code can't call unmanaged directly, so you need wrapper functions to handle the memory management issues and to translate between .NET objects and the data structures of your application. From the link above, check out the section on "How to: Wrap Native Class for Use by C#."

Here is a solution. The solution allows to call C# function from C by decorating your function with [DllExport] attribute (opposite of P/Invoke DllImport).
https://sites.google.com/site/robertgiesecke/Home/uploads/unmanagedexports
C# code
class Test
{
[DllExport("add", CallingConvention = CallingConvention.StdCall)]
public static int Add(int left, int right)
{
return left + right;
}
}
C code
int main()
{
int z = add(5,10);
printf("The solution is found!!! Z is %i",z);
return 0;
}