AutoMapper: UseValue vs ResolveUsing vs MapFrom
I just hit a confusing mapping bug whilst using AutoMapper to map DateTime.Now to a field in my database. Every item that was being added to the database had the same value in the "DateAdded" - to the millisecond. This was because I was using the following mapping expression: Mapper.CreateMap<SourceObject, DestObject>() .ForMember(m => m.DateAdded, o => o.UseValue(DateTime.Now)); UseValue() retrieves a value on first-run and stores it in the mapping (hence the static DateTime value that's being stored in the database), whereas ResolveUsing() resolves at run-time - which is obviously why it's called Resolve Using(). A minor oversight, but confusing nonetheless. Use ResolveUsing(s => {}) when you want to resolve a destination field from a derived value. This should be used for any DateTime mappings, and any more complicated mapping functions. Use MapFrom(s => s.MemberName) when you return an actual source object member. Use UseValue() if you