Passing C# Objects' References to C++ DLL and vice versa

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I wish to know how to to pass the reference of an object of C# to C++ and Manipulate it in C++.

For example, I have a class in C#,

C#

class StudentScore
    
{
    
protected:
    
    int Maths;
    
    int Science;
    
    int Social;
    
    
    
public:
    
    int GetAverageScore()
    
    {
    
    return ((Maths+Science+Social)/3)
    
    }
    
    
    
    void SetMaths(int score)
    
    {
    
    Maths = score;
    
    }
    
    void SetScience(int score)
    
    {
    
    Science= score;
    
    }
    
    
    
    void SetSocial(int score)
    
    {
    
    Social= score;
    
    }
    
}

The object of StudentScore will be created in C# and values will be assigned as follows

C#

refObjStudentScore = new StudentScore(); 
SetMaths(85);
SetScience(80);
SetSocial(90);

Now I wish to pass the reference of object

C#

refObjStudentScore

to a C++ DLL and invoke the function

C#

GetAverageScore

to get average score in C++.

Could you please let me know how to achieve this.

Also, as a next step, I wish to pass collection of StudentScore to C++.

Any hint on this front will be of great help to me.

Posted 13-Jul-13 19:18pm

Prashant_Patil_

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Sergey Alexandrovich Kryukov · Answer 1 · 2013-07-13T19:29:00

You cannot do it in any simple way. Typically, for interfacing between .NET assemblies and native DLLs, only primitive types, structures, as well as some select classes are used. Such classes, such as System.String, may have some predefined marshaling to a number of unmanaged types. The interfaced method itself should be a static method of some .NET class, which is equivalent to a "regular" (not object-oriented) C++ methods.

At the same time, you can use some managed classes, if they are the parameters of methods. For some, default marshaling is defined, for others, you can create custom marshaling. I would call it a pretty advanced topic. Please start here:
http://msdn.microsoft.com/en-us/library/d3cxf9f0%28v=vs.90%29.aspx[^].

—SA

H.Brydon · Answer 2 · 2013-07-13T20:11:00

What you want to do is use C++/CLI instead of plain C++. This will give you access to all of the managed types and libraries in the CLI. To make it easy, anything that is to be common between C# and C++ should be written on the C# side and #import'ed by C++ (this can be done by defining on the C++ side but is much more complicated to explain here).

Easiest route: make your executable managed (C# if possible) and each of the DLLs can be C# or C++/CLI (or VB.NET, yecch!).

Passing C# Objects' References to C++ DLL and vice versa

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