AutoMapper Custom Value Resolvers async - asp.net-core

Question

I want to convert BotViewModel to Bot using AutoMapper.
There is an example input below from type BotViewModel. If I want to add a new bot to the database, that model should be matched/mapped to Bot model and Bot's foreign keys should be resolved.
In other words, BotViewModel.Symbol should be matched to CryptoPair.Symbol and BotViewModel.Interval to TimeInterval.Interval.
{
"id": 0,
"name": "Bot 1",
"status": true,
"symbol": "LTCBTC",
"interval": 6
}
My code below is working exactly as I described it above. It uses http://docs.automapper.org/en/stable/Custom-value-resolvers.html. The thing is that I want to make _context.CryptoPairs.FirstOrDefault async FirstOrDefault => FirstOrDefaultAsync.
I want to do that because I feel like that's not the best practice. Basically, I'm looking for an advice if that's okay or not. By the way, if the symbol or interval cannot be matched because it simply doesn't exist in the database, var bot = _mapper.Map<Bot>(botViewModel); should just throw an exception which is later handled by my controller.
public class CryptoPairResolver : IValueResolver<BotViewModel, Bot, int>
{
private readonly BinanceContext _context;
public CryptoPairResolver(BinanceContext context)
{
_context = context;
}
public int Resolve(BotViewModel source, Bot destination, int destMember, ResolutionContext context)
{
return _context.CryptoPairs.FirstOrDefault(p => p.Symbol == source.Symbol).Id;
}
}
public class TimeIntervalResolver : IValueResolver<BotViewModel, Bot, int>
{
private readonly BinanceContext _context;
public TimeIntervalResolver(BinanceContext context)
{
_context = context;
}
public int Resolve(BotViewModel source, Bot destination, int destMember, ResolutionContext context)
{
return _context.TimeIntervals.FirstOrDefault(i => i.Interval == source.Interval).Id;
}
}
public class MappingProfile : Profile
{
public MappingProfile()
{
CreateMap<BotViewModel, Bot>()
.ForMember(dest => dest.CryptoPairId, opt => opt.MapFrom<CryptoPairResolver>())
.ForMember(dest => dest.TimeIntervalId, opt => opt.MapFrom<TimeIntervalResolver>());
}
}
Models:
public class Bot
{
public int Id { get; set; }
public string Name { get; set; }
public bool Status { get; set; }
public int CryptoPairId { get; set; }
public CryptoPair CryptoPair { get; set; }
public int TimeIntervalId { get; set; }
public TimeInterval TimeInterval { get; set; }
}
public class BotViewModel
{
public int Id { get; set; }
public string Name { get; set; }
public bool Status { get; set; }
public string Symbol { get; set; }
public KlineInterval Interval { get; set; }
}
public class CryptoPair
{
public int Id { get; set; }
public string Symbol { get; set; }
public List<Bot> Bots { get; set; }
}
public class TimeInterval
{
public int Id { get; set; }
public KlineInterval Interval { get; set; }
public List<Bot> Bots { get; set; }
}
Edit:
public async Task<Bot> CreateAsync(BotViewModel botViewModel)
{
// Map BotViewModel to Bot
var cryptoPair = await _context.CryptoPairs.FirstOrDefaultAsync(e => e.Symbol == botViewModel.Symbol);
if (cryptoPair == null)
{
throw new BadRequestException();
}
var timeInterval = await _context.TimeIntervals.FirstOrDefaultAsync(e => e.Interval == botViewModel.Interval);
if (timeInterval == null)
{
throw new BadRequestException();
}
var bot = new Bot
{
Name = botViewModel.Name,
Status = botViewModel.Status,
CryptoPairId = cryptoPair.Id,
TimeIntervalId = timeInterval.Id
};
// Create code
_context.Bots.Add(bot);
await _context.SaveChangesAsync();
return bot;
}