public string SetPrefix(IGuild guild, string prefix) { if (string.IsNullOrWhiteSpace(prefix)) { throw new ArgumentNullException(nameof(prefix)); } if (guild == null) { throw new ArgumentNullException(nameof(guild)); } prefix = prefix.ToLowerInvariant(); using (var uow = _db.UnitOfWork) { var gc = uow.GuildConfigs.For(guild.Id, set => set); gc.Prefix = prefix; uow.Complete(); } Prefixes.AddOrUpdate(guild.Id, prefix, (key, old) => prefix); return(prefix); }