Question

I have an unmanaged dll with a class “MyClass” in it.
Now is there a way to create an instance of this class in C# code? To call its constructor? I tried but the visual studio reports an error with a message that this memory area is corrupted or something.

Thanks in advance

Answer 1

C# cannot create class instance exported from native Dll. You have two options:

1. Create C++/CLI wrapper. This is .NET Class Library which can be added as Reference to any other .NET project. Internally, C++/CLI class works with unmanaged class, linking to native Dll by standard C++ rules. For .NET client, this C++/CLI class looks like .NET class.

2. Write C wrapper for C++ class, which can be used by .NET client with PInvoke. For example, over-simplified C++ class:

    class MyClass()
    {
    public:
        MyClass(int n){data=n;}
        ~MyClass(){}
        int GetData(){return data;}
    private:
        int data;
    };

C API wrapper for this class:

    void* CreateInstance()
    {
        MyClass* p = new MyClass();
        return p;
    }

    void ReleaseInstance(void* pInstance)
    {
        MyClass* p = (MyClass*)pInstance;
        delete p;
    }

    int GetData(void* pInstance)
    {
        MyClass* p = (MyClass*)pInstance;
        return p->GetData();
    }

    // Write wrapper function for every MyClass public method.
    // First parameter of every wrapper function should be class instance.

CreateInstance, ReleaseInstance and GetData may be declared in C# client using PInvoke, and called directly. void* parameter should be declared as IntPtr in PInvoke declaration.