Why my code doesn't evaluate an "if" statement?

I am currently making a code for a project (using WinApi), in which I must save data such as contact information and apointments in a binary file. Everything works except the saving part. In the code below while running it doesn't evaluate the if statement --if (myFile.is_open()) {}-- it just "skips" it, asi if it were not even there.

** "myFile" being a fstream type variable.

void guardareg(Registros *inicio)
{
    myFile.open("myList.bin", ios::out | ios::trunc |
    ios::binary);
if (myFile.is_open()) {
    Registros *temp = inicio;
    while (temp != NULL)
    {
        myFile.write(reinterpret_cast<char *>(temp),
            sizeof(Registros));
        temp = temp->sig;
    }
    myFile.close();
                      }
return;
}