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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.

andengine for c sharp

I've come across some discussion about C# and Java and it seems that a lot of programmers here in StackOverflow like C# more than java. Look here
I'm just curious if I can use the andegine library in C# using mono?
OR to be precise can I use java libraries in C# when creating an android application?
Is there a disadvantage of using C# instead of Java and if it is possible to use a Java library in C#, can you give me some example? I'm quite confused.

If you wish to use a Java library you should use Java.
It isn't possible to directly use a Java library from C#, but if you want to use C# you could:
Find a similar library that is written for .NET.
Andengine is open source. You could choose to port it to C#, though this would take a long time.

How to compile java code from a .net application?

I am creating a source code editor for Java using C# in .NET 4. I need to know how I can interact with the jre to compile the java code on my application editor interface from .net. I wish to display the user any errors on the code as well. Any ideas on how to accomplish this will be greatly appreciated.

Note that the JRE is the runtime, and as such doesn't come with the compiler. You will require the JDK to compile.
I think the simplest solution is to spawn off an instance of javac from within your .Net application. Perhaps a preferable solution (however) would be to write your app in Java itself, and you can then make use of the Java compiler API directly within your app.

Perhaps the most natural interoperability method is to run the Java code in a JVM, the .NET code in a CLR, and use a runtime bridge to manage the communications between them. In this scenario, the .NET code calls .NET classes and objects that act as proxies for the Java classes and objects. The proxies manage the communication; the calling .NET classes aren't even aware that they're ultimately calling Java classes. A runtime bridge provides interoperability for a wide variety of architectures, because the Java code and the .NET code can be on different machines, the Java code can run in a standalone JVM or in a Java EE application server, and the solution provides interoperability for any JDK version. As with bytecode translation solutions, you need only the Java bytecodes, not the source.
The code for this article uses JNBridgePro from JNBridge.

Reverse PInvoke and create a full unmanaged C# program

I know this is a strange question but the idea is simple: I prefer C# syntax rather than C++:
-Setters and getters directly inside a property
-interfaces
-foreach statement
-possibility to declare an implicit cast operator
other small things...
What I really don't know is if is possible to import a c++ dll (expecially std libraries) in C# if I don't use any namespace (even System)
The idea is just to write a program using everything that you will normally use in C++ (nothing from CLR so), even printf for example
Thanks for any answer

No it is not possible to simply import existing C or C++ files into a C# project. They are very different languages and cannot be mixed at the source level.
The way to mix C# and C++/C applications is at the PInvoke or COM Interop level. This works by duplicating the signatures in C# and allowing the C# compiler to determine the binary layout of the native type in order to marshal between the languages.

There's now something close to this
.NET Native compiles C# to native machine code that performs like C++. You will continue to benefit from the productivity and familiarity of the .NET Framework with the great performance of native code.
It's for Windows Store apps only (desktop apps may come in the future):
Desktop apps are a very important part of our strategy. Initially, we are focusing on Windows Store apps with .NET Native. In the longer term we will continue to improve native compilation for all .NET applications.
And
apps will get deployed on end-user devices as fully self-contained natively compiled code (when .NET Native enters production), and will not have a dependency on the .NET Framework on the target device/machine

No; this is not directly possible. In particular, C++ templates are not supported by C#.

C#/.NET scripting library

I want to enhance an application with scripting support like many other applications have, e.g. MS Office using VBA or UltraEdit using JavaScript.
Which libraries do exist for C#/.NET (and which language(s) do they support)?

Please check CS Scripting library
Here is an article about scripting Photoshop CS with C#
This one discusses using LUA as scripting lib with C#.

IronPython is a dynamic .NET scripting language.
IronPython is an implementation of the Python programming language running under .NET and Silverlight. It supports an interactive console with fully dynamic compilation. It's well integrated with the rest of the .NET Framework and makes all .NET libraries easily available to Python programmers, while maintaining compatibility with the Python language.
See IronPython embedding for examples showing ways to call IronPython from .NET apps.
The IronPython Calculator and the Evaluator goes into the details of using IronPython from a C# application.

Lua is often touted as being one of the better ones... Try looking at this other question for more information: What are the most effective ways to use Lua with C#?
Also:
Lua Interface
Binding code to Lua

See "What is the best scripting language to embed in a C# desktop application."
Also see "It Already Is A Scripting Language" from Eric Lippert.

Don't forget LSharp, LISP in .NET. Something to keep an eye on if you are exploring functionality stage. Maybe Rob Blackwell will be glad to hear you're considering it.

You can bake your own scripting environment with Mono.CSharp (just one simple dll) or Roslyn, both are getting quite mature now.
Mono contains the Evaluator class and Roslyn the ScriptEngine, both make it a breeze setting up a script environment. Of course something like ScriptCS already builds on that (Roslyn) and gives you more features.
For an C# script environment built on Mono.CSharp you can check out CShell (which I made).

Depending on your needs, the SILK library might be a good option.
It's an easy to use interpreter. The interpreted language is not C#. It's a custom language that was designed to be easy to use (very little punctuation, not case sensitive, etc.) But it does support functions.
Built-in functions are handled via events. That is, when the interpreted code calls one of your internal functions, it raises an event in your program.