ref class и vector

#include <iostream>
#include <string.h>
#include <vector>
 
ref class Book {
private:
    double cost;
    System::String^ autor;
    System::String^ name;
    System::String^ janr;
 
public:
    Book(double st, System::String^ au, System::String^ na, System::String^ ja) {
        cost = st;
        autor = au;
        name = na;
        janr = ja;
    
    }
    ~Book() {
    }
 
    double getC() {
        return cost;
    }
};
 
int main() {
    std::vector <Book> libra;
    Book element(12.5, "dsfsd", "rsdf", "ewfsd");
    libra.push_back(element);
}

int main() {
    System::Collections::Generic::List<Book>^ libra = gcnew System::Collections::Generic::List<Book>();
    Book element(12.5, "dsfsd", "rsdf", "ewfsd");
    libra->Add(element);
}

using namespace System::Collections::Generic;

int main() {
    List<Book>^ libra = gcnew List<Book>();
    Book element(12.5, "dsfsd", "rsdf", "ewfsd");
    libra->Add(element);
}

List<Book^> libra = gcnew List<Book>();

List<Book^> libra = gcnew List<Book>();

List<Book^> libra = gcnew List<Book^>();

List<Book^> libra = new List<Book^>();

List<Book^> ^libra = gcnew List<Book^>();

    List<Book^>^ libra = gcnew List<Book^>();
    Book^ element = gcnew Book(12.5, "dsfsd", "rsdf", "ewfsd");
    libra->Add(element);

libra[0]->smth