public Guid AddExchangeRate(AddExchangeRateCommand command)
 {
   var exchangeRate = new ExchangeRate()
   {
     ExchangeRateId = Guid.NewGuid(),
     Price = command.Price,
     Name = command.Name
   };
   _exchangeRateService.Insert(exchangeRate);
   _unitOfWork.SaveChanges();
   return exchangeRate.ExchangeRateId;
 }
 private void Save(ExchangeRateModel model)
 {
   if (model.ExchangeRateId == Guid.Empty)
   {
     var createCommand = new AddExchangeRateCommand(model.Name,model.Price);
     model.ExchangeRateId = _exchangeRateCommandService.AddExchangeRate(createCommand);
   }
   else
   {
     var updateCommand = new EditExchangeRateCommand(model.ExchangeRateId,model.Name, model.Price);
     _exchangeRateCommandService.EditExchangeRate(updateCommand);
   }
 }