How to ignore mapping with condition - asp.net

Question

As I'm having a single DTO, we use DTOs for GET, PUT and POST http method in our Web API.
To make simple we have ActivityDO:
public ActivityDTO
{
public int Id;
public string Name;
public string CategoryName;
public DateTime DateCreated;
public DateTime DateModified;
}
The challenge is when you only have a single DTO for handling multiple conditions i.e. post/get/put method, the mapping as follow:
private MapperConfiguration configuration = new MapperConfiguration(cfg => {
cfg.CreateMap<ActivityDTO, Activity>()
.ForMember(dst => dst.UserId, opt => opt.MapFrom(src => HttpContext.Current.User.Identity.GetUserId()))
.ForMember(dst => dst.CategoryId, opt => opt.MapFrom(src => GetCategoryId(HttpContext.Current.User.Identity.GetUserId(), src.CategoryName)))
.ForMember(dst => dst.DateCreated, opt => opt.MapFrom(src => DateTime.UtcNow))
.ForMember(dst => dst.DateModified, opt => opt.MapFrom(src => DateTime.UtcNow));
});
I want to IGNORE the mapping for DateCreated if we do the update and we can do the condition if the id <= 0, the rest is allowed to mapping for DateCreated.
Is this possible? Would rather to have a seperate DTOs between GET/POST (Add) VS PUT (Update)? Is there any better solution to handle this DateCreated VS DateModified thingy?
I'm appreciated your feedback/comment.

Answer 1

This is the way to add conditions.
Is that what you are looking for?
private MapperConfiguration configuration = new MapperConfiguration(cfg => {
cfg.CreateMap<ActivityDTO, Activity>()
.ForMember(dst => dst.UserId, opt => opt.MapFrom(src => HttpContext.Current.User.Identity.GetUserId()))
.ForMember(dst => dst.CategoryId, opt => opt.MapFrom(src => GetCategoryId(HttpContext.Current.User.Identity.GetUserId(), src.CategoryName)))
.ForMember(dst => dst.DateCreated, opt => opt.MapFrom(src => src.Condition(src.DateCreated != null)))
.ForMember(dst => dst.DateModified, opt => opt.MapFrom(src => DateTime.UtcNow));
});
I used src.DateCreated != null but you can specify any condition using the src.Condition() and the variable will only be mapped when the condition is met.
Also
You can use AutoMapper's PreCondition
var configuration = new MapperConfiguration(cfg => {
cfg.CreateMap<Foo,Bar>()
.ForMember(dest => dest.baz, opt => {
opt.PreCondition(src => (src.baz >= 0));
opt.MapFrom(src => {
});
});
});