[Programming] Passing String from C# to C++

I'm writting code for KTX-PC in C# and I have VSRC003SDK written in C++....,

My first approach was...,
C#:  string -> char*  => C++: char* -> tchar*

Since the methods in SDK takes tchar*, I have to find the way to convert into txhar*....
Following is the way I did:
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C++:

       bool Init(System::IntPtr fpathIntPtr, int fpathLength){

             

char * fpathCharPtr = (char *)fpathIntPtr.ToPointer();

              //convert unsigned char * to tchar *

              //Get the size of the string by setting 4th parameter to -1

              int len = MultiByteToWideChar(CP_ACP, 0, fpathCharPtr, -1, NULL, 0);

             

              //allocate space fpr wide char string

              wchar_t* fpath = new wchar_t[len];

              if(!fpath)

              {

                     delete []fpath;

              }

              //convert

              MultiByteToWideChar (CP_ACP, 0, fpathCharPtr, -1, fpath, len );

                    

              //load init motion and play the motion

             

              if(VSRC003_LoadMotion(fpath)){ System::Console::WriteLine("Failed to load the init motion."); return false;}

              if(VSRC003_PlayMotion(0)){ System::Console::WriteLine("Failed to play the init motion.\n\n"); return false;}

              else System::Console::WriteLine("Starting init motion.\n\n");

                     //release memory for fpath

              delete []fpath;

         
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The conversion part worked fine....
Now I was trying to find the way to convert string to char* in C#.
....
....
......

I tried everything I could find online and nothing worked...
by the way..., I spent three days...

Then, I decide to do it in different way!
C#:  string -> IntPtr  => C++: IntPtr -> char* -> tchar*

Wow!
Do not try converting IntPtr -> char*...
conversion from IntPtr returns unicode, not ascii!!!

Therefore..., try IntPtr -> tchar* !!!
 ---------------------------------------------------------------------------------
C#:

static void Main(string[] args)

        {

            Vsrc003Wrapper vsrc003Wrapper = new Vsrc003Wrapper();

            string fpath = "init.txt";

            IntPtr fpathIntPtr = Marshal.StringToHGlobalAuto(fpath);

           

            vsrc003Wrapper.Init(fpathIntPtr, fpath.Length);

            Marshal.FreeHGlobal(fpathIntPtr);

C++:

bool Init(System::IntPtr fpathIntPtr, int fpathLength){

      

       wchar_t * fpath = reinterpret_cast<wchar_t*>(fpathIntPtr.ToPointer());

                                        

       //load init motion and play the motion

       if(VSRC003_LoadMotion(fpath)){ System::Console::WriteLine("Failed to load the init motion."); return false;}