Return from C# lib a structure containing a string to c++ program

I am trying to call a C# lib from a C++ program. C# and this interop is pretty new for me. Some of the communications have been easy until I had to face strings inside structures. I have been reading a lot and saw several examples, but I am unable to replicate them and make them work.

I extracted the code with the example of sending a string, and retriving the string which works (_string_exchange). And the method _return_struct which returns a struct with a string that doesnt works. Debugger fails when I try to use the variable for std::cout, with an unhandled exception from 0x00007FFFEA98A388 (KernelBase.dll). The Console.WriteLine havent wrote anything during the call.

I assume this is a problem matching the scrutures. Both are compiled in release x64, using .NET Framework 4.6.1. Also I have been checking with sizeof() and Marshal.SizeOf() to check that both have the same byte length. Also tried to change c++ project character from unicode to multibyte without success.

I saw examples like this that were pretty good explaning everything, but I dont know what I am missing: Passing strings/arrays within structures between C++/C#

C++ program:

struct myStruct
{
    int myInt;
    double myDouble;
    bool myBool;
    char myString[64];
}; 

int main() {
    const TCHAR* pemodule = _T("F:\\PATH\\TO\\DLLsi\\LibCSharp.dll");
    HMODULE lib = LoadLibrary(pemodule);

    typedef LPCSTR(_cdecl *_string_exchange)(LPCSTR s);
    auto pString_exchange = (_string_exchange)GetProcAddress(lib, "_string_exchange");
    LPCSTR test = pString_exchange("LPCSTR test works fine");
    std::cout << test << std::endl;

    typedef myStruct(_cdecl *_return_struct)();
    auto pReturn_struct = (_return_struct)GetProcAddress(lib, "_return_struct");
    myStruct aStruct = pReturn_struct();
    std::cout << aStruct.myString << aStruct.myBool << " " << aStruct.myDouble << " " << aStruct.myInt << std::endl;

    return 0;
}

C# library:

namespace LibCSharp
{    
    public class Class1
    {
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
        public struct myStruct
        {
            public int myInt;
            public double myDouble;
            [MarshalAs(UnmanagedType.U1)]
            public byte myBool;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 64)]
            public string myString;
        }

        [DllExport]
        public static myStruct _return_struct()
        {
            Console.WriteLine("test");
            myStruct a;
            a.myInt = 3;
            a.myDouble = 2;
            a.myBool = 1;
            Console.WriteLine(a.myBool);
            a.myString = "Hello world! My values are: ";//28
            Console.WriteLine(a.myString);
            return a;
        }

        [DllExport]
        public static string _string_exchange(string s)
        {
            Console.WriteLine(s);
            return s;
        }
    }
}

I am also aiming in a future to make this structure an array, I hope once this is solved I wont face much problems, but any comment in advance is also wellcome.

Thank you in advance