public bool checkPersonExistence(personaModel persona)
 {
     try
     {
         DDBBGateway data = new DDBBGateway();
         data.prepareQuery(
             "select count(*) from Personas " +
             "inner join Usuarios on Personas.id = Usuarios.idPersona " +
             "where Personas.dni = '" + persona.dni + "' and Usuarios.mail = '" + persona.user.mail + "';");
         if (data.sendScalarQuery() <= 0)
         {
             return(false);
         }
         else
         {
             return(true);
         }
     }
     catch (Exception ex)
     {
         throw ex;
     }
 }