Develop Reference

How to call a c# dll from java program

I have a c# dll that needs to be called in Java.I see that there is a method using jni to call c++ dlls.How can I do it for a c# dll..Please help..I couldnt find any good material on this

From here:-
IKVM.NET is an implementation of Java for Mono and the Microsoft .NET
Framework. It includes the following components:
A Java Virtual Machine implemented in .NET
A .NET implementation of the Java class libraries
Tools that enable Java and .NET interoperability

You can use Java Native Interface. Or you can create a COM assembly from the C# code and use J-Interop to invoke it.
If you have C# dll sources you need to use maybe the better way will be to translate it to Java using some tools like GrassHopper.
According to GrassHopper key feature explanation it can convert MSIL to Java bite code. So can use without sources of c# dll

Check this: http://www.javonet.com
If you look for quick and easy solution then Javonet should work fine for you. It is light counterpart of IKVM and J-Integra works also as native bridge.
All you have to do is:
add Javonet.jar do your project call
call Javonet.addReference("yourlib.dll")
use your .NET library like it was almost JAVA package
Sample:
NObject obj = Javonet.New("yourDotNetClass");
obj.invoke("YourMethod","arg1", 2);
The syntax is not strongly-typed and works like reflection but gives you fastest access to any custom .NET code, third-party libs or .NET framework as no changes are needed on .NET side. If you need it is also possible to implement custom strongly-typed wrappers.
I do recommend this bridge as in my opinion it is easiest to quickly get things done but also other native bridges are worth checking as this is best approach for such case.
I would avoid going into custom JNI or COM unless you have a lot of time and you just want to learn, if you need quick and reliable solution take one of third-party bridges.

Automatic conversion of C++ API to C#?

I am wondering if there is something like automatic conversion/wrapper code generation of a c++ API to C#?
Specifically I am seeking a way to call the Remote Desktop Services API from C#.

A suggestion: C++/CLI.
Using the C++/CLI you can use the libraries written in C/C++ to C/C++ along with of the .net libraries/dll's. More information:
A first look at C++/CLI

No you definitely need to create an interop code.
If it's a COM api there is some sort of support for using it directly with C#

You might try either decompiling RDCMan (http://www.microsoft.com/download/en/details.aspx?id=21101), it does it. Or there is an open source project on Codeplex that does it as well.
http://terminals.codeplex.com/
EDIT:
There is also a tool that Microsoft provides call aximp (http://msdn.microsoft.com/en-us/library/8ccdh774(v=VS.100).aspx). If you run aximp.exe {{path_to}}\mstscax.dll, it will generate a .NET WinForms control library that wraps the ActiveX control.

How to use C# code in C++ project

I have some code in C# which I want to use in other project (coded in C++).
From what I researched, I need to create a .lib but MSVS only creates .dll (I think..). I think is possible to use the .dll by using LoadLibrary() over C++ but seems not very friendly.
1 - Can I create the .lib in MSVS? If not, how can I create it.
2 - What is the best way to integrate the code? By the .lib or using .dll + LoadLibrary()?

The easiest option, honestly, is to use C++/CLI. That lets you use both object systems (.NET, and traditional C++ with its standard template library).

Is it managed C++ ? If so you can directly add a reference to the C# dll and use it.

What you need is a com compliant class in c#:
http://en.allexperts.com/q/C-3307/2008/2/Using-C-class-C.htm
http://blogs.msdn.com/b/deeptanshuv/archive/2005/06/26/432870.aspx

One possibility is to make your C# code Managed COM compliant. Then use the standard COM api's (QueryInterface etc) to call the C# COM code.
The codeproject sample may be useful
http://www.codeproject.com/KB/cs/ManagedCOM.aspx

Using DirectX DLL (C++) from C#

I have a native C++ DLL using DirectX, that I want to be able to use through C# to be able to create content creation tools.
Adding COM would require quite an effort it seems.
Can P/Invoke be used to maintain classes using polymorphism, or would it require me to wrap most of the code to facilitate use of P/Invoke?
It there a better solution is available? Or should I even consider writing the tools in C++ using Qt perhaps?

I always feel that C++/CLI is always the best option when doing C# to C++ interop. You can easily create thin wrappers for an unmanaged library that will look exactly like a managed library to your C# code. It also gives you more control over how marshaling and pinning is performed.
There are ways to automatically generate C++/CLI I believe, but I've never used them.
More info on C++/CLI here:
http://msdn.microsoft.com/en-us/magazine/cc163681.aspx

I presume rendering with D3D directly from C# isn't an option? (because that certainly would be easier!)
A long time ago, I used SWIG to automatically maintain C# "bindings" of my C++ rendering DLL code. It uses P/Invoke to expose the C++ objects on the C# side, and you won't have to maintain that code anymore.

You don't need to write wrap on QT.
I advice you to write Observer class both in C# & C++, and hide calls of Native functions to it.
Schema is like this
Your code in C# -> Observer(C#) -> Native call to Observer(C++) -> Calls to your dll.

Creating C++ Dll, and call it from C#

In my project I got a device which comes with C++ Sample codes. The codes are ok and the device is working as expected.
But I need it to talk with my C# interface because all other devices are currently using C# interface.
So I am planning to create a DLL Wrapper for the driver. I will create a C++ Library of my own (from source code with proper interface) and Call this C++ Library from C# using DLLImport (just call my interfaces there.).
I am pretty sure it can be done this way, but I have never created a C++ Library and used it from C# yet. So, can anyone refer me to some tutorial that goes with my problem?
I am using C++/C# int VS.NET 2008.
Regards,
Maksud

Have a look at
using a class defined in a c++ dll in c# code

Another useful tool you have at your disposal is C++ CLI.
You can use C++ CLI to create an intermediate library - one that exposes managed classes but runs unmanaged C++ code. You can actually mix managed and unmanaged C++ in the same DLL.
The unmanaged portion can accesses the unmanaged DLLs without having to use the PInvoke functions.
Your C# code can access the managed classes in this intermediate library.

Depending on the DLL and what you need to do you may not need to create a wrapper directly. You might be able to get away with P/Invoke for the functions. You will need to evaluate your specific needs and what is already available in the libraries/code provided.

For anyone who comes to this question and are looking for answers, you may want to try xInterop NGen++ , a C# wrapper generator for native C++ DLL, which has been just released to the public, the tool can generate C# wrapper for native C++ DLL automatically and instantly by using advanced P/Invoke technologies. Check out the current version and a free version will be out soon.
(I am the author of the tool)