We are writing a wrapper in Managed C++. Wrapper is based on a C dll.
That wrapper will be used from .Net based application and VB also.

Our initial understanding that a .NET Application developer will pass
a delegate to the Managed C++ wrapper and in this wrapper, we have to
cast the delegate into function pointer.  The argument list of that
function pointer is not compatible in .NET.

A .NET developer will pass a delegate to get the desired output. Is
their any other way?

.Please guide, how we will write wrapper for the following C Code?

SetProgressProc(void * userdata, ProgressProc callback);

// message callback proc
typedef  void __stdcall MessageProc(
    const void * context, // IN: message proc context
    MyString & text, // OUT: message text
    int & number); // OUT: message number

// progress callback proc
typedef  bool __stdcall  ProgressProc( // RETURN: cancel operation?
    double progress, // IN: fractional progress (0.0 .. 1.0)
    const void * userdata, // IN: progress callback userdata
    const void * context, // IN: message proc context
    MessageProc * message, // IN: message proc; else 0
    unsigned int step, // IN: global step number (1 .. count)
    unsigned int count); // IN: global step count

struct MyString
{
    enum Type // encoding type
    {
        Type_ASCII = 1, // local encoding (8-bit)
        Type_UTF8 = 2, // Unicode (8-bit)
        Type_Wide = 3, // Unicode (wchar_t)
    };

Type type; // encoding type
    size_t size; // size of string data buffer in characters
    void * data; // pointer to string data buffer
};