How to use C++ class with C#

[Mukesh Motwani]

I have a class library written in C++ which I intend to use in a program whose interface is designed in C#. I understand that I need to create an unmanaged DLL and use the DLL in the program. Are there any resources which show how to create a unmanaged C++ DLL in .NET environment without using MFC and how I could use the DLL with C#? MSDN site suggests wrapping the unmanaged DLL function in a managed class but doesnt give any much useful information.

Thanks
Mukesh

[Clay Burch]

Here is a Microsoft link explaining how to use P/Invoke with DLLImport to access functions in unmanaged DLLs.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconconsumingunmanageddllfunctions.asp

If you have a active X library (an OCX or ATL DLL)you are trying to use, then you can create the .NET wrapper class using the tool aximp.exe.

[Mukesh Motwani]

I created an unmanaged DLL which has a C++ class.
PInvoke is able to access global exported DLL functions but it CANNOT import class methods from an unmanged DLL. Thus, I get an error "Object reference not set to an instance of an object" because I am not able to create an object of my class. In VC++ 6 I could use the header file and create an instance. But C# doesnt allow that. In fact,

[DllImport("mywin32.dll")]
public static extern Cwin32class();

is not compiled because the compiler thinks that method has no return type! But constructors are not supposed to have return types. Thus I cant find any way of using my unmanaged object oriented classes with the C# UI. Can anyone help me please?

Thanks
Mukesh

[Michael]

Mukesh,

I have the same problem when I try to use a C++ DLL. Have you found out what the problem could be and how to instantiate the wrapper class or the object?

Regards.

Michael.

> I created an unmanaged DLL which has a C++ class.
> PInvoke is able to access global exported DLL functions but it CANNOT import class methods from an unmanged DLL. Thus, I get an error "Object reference not set to an instance of an object" because I am not able to create an object of my class. In VC++ 6 I could use the header file and create an instance. But C# doesnt allow that. In fact,
>
> [DllImport("mywin32.dll")]
> public static extern Cwin32class();
>
> is not compiled because the compiler thinks that method has no return type! But constructors are not supposed to have return types. Thus I cant find any way of using my unmanaged object oriented classes with the C# UI. Can anyone help me please?
>
> Thanks
> Mukesh