Somehow my code doesn't work any more (it did work before with the exact same code). This is the problem:
The code
I'm trying to map some objects to ViewModels with this code:
Configuration:
Mapper.CreateMap<BookcaseItem, FoundBookcaseItemViewModel>()
.ForMember(x => x.Title, opt => opt.MapFrom(src => src.Book.Title))
.ForMember(x => x.Authors, opt => opt.MapFrom(src => src.Book.Authors.Select(x => x.Name).Aggregate((i, j) => i + ", " + j)))
.ForMember(x => x.Identifiers, opt => opt.MapFrom(src => (!string.IsNullOrEmpty(src.Book.Isbn10) ? ("ISBN10: " + src.Book.Isbn10 + "\r\n") : string.Empty) +
(!string.IsNullOrEmpty(src.Book.Isbn13) ? ("ISBN13: " + src.Book.Isbn13) : string.Empty)))
.ForMember(x => x.Pages, opt => opt.MapFrom(src => src.Book.Pages))
.ForMember(x => x.ImageUri, opt => opt.MapFrom(src => src.Book.ThumbnailUriSmall));
The usage:
public ActionResult Index()
{
string facebookId = _accountService.GetLoggedInUserFacebookId();
IEnumerable<BookcaseItem> items = _bookcaseItemService.GetBookcaseItemsForUser(facebookId);
IEnumerable<FoundBookcaseItemViewModel> viewModels = items.Select(Mapper.Map<BookcaseItem, FoundBookcaseItemViewModel>);
return PartialView(viewModels);
}
The error
This results in the following error:
An exception of type 'AutoMapper.AutoMapperMappingException' occurred in AutoMapper.dll but was not handled in user code
The debug data
First of all I ensure that there are no configuration errors by calling:
Mapper.AssertConfigurationIsValid();
I've set breakpoints all over my code and try to debug it, but I can't make sense of it. The 'items' collection is filled with data (proxy classes generated by Entity Framework), but the the 'viewModels' collection is filled with strange data. It has a 'message' that says this:
Mapping types: BookcaseItem_B9B52593B2659AC05C47AB2A6E0F7AEA9989CC34D3527DF5B6AA988ED57166FB -> String System.Data.Entity.DynamicProxies.BookcaseItem_B9B52593B2659AC05C47AB2A6E0F7AEA9989CC34D3527DF5B6AA988ED57166FB -> System.String
Destination path: FoundBookcaseItemViewModel.Authors
Source value: System.Data.Entity.DynamicProxies.BookcaseItem_B9B52593B2659AC05C47AB2A6E0F7AEA9989CC34D3527DF5B6AA988ED57166FB
And then there's a stacktrace property that says:
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at System.Linq.SystemCore_EnumerableDebugView`1.get_Items()
Oh and finally there's another property called 'context' with the following data:
Can anyone explain what's going on here and why my code isn't working any longer? I did a couple of changes to my solution recently, but I've rolled them back by Git, so they shouldn't have any effect on the code.
My setup
The entity and ViewModel
I don't know if it's relevant, but here is the source class for the mapping:
public class BookcaseItem : Entity
{
public Guid Id { get; set; }
public bool IsRenting { get; set; }
public bool IsSwapping { get; set; }
public bool IsSelling { get; set; }
public decimal RentingPrice { get; set; }
public decimal SellingPrice { get; set; }
public string Currency { get; set; }
public bool IsAvailable { get; set; }
public virtual Guid BookId { get; set; }
public virtual Guid UserId { get; set; }
public virtual Book Book { get; set; }
public virtual User User { get; set; }
public BookcaseItem()
{
IsAvailable = true;
Currency = "USD";
}
}
And this is the destination class for the mapping:
public class FoundBookcaseItemViewModel
{
public Guid Id { get; set; }
public bool IsRenting { get; set; }
public bool IsSwapping { get; set; }
public bool IsSelling { get; set; }
public decimal RentingPrice { get; set; }
public decimal SellingPrice { get; set; }
public string Title { get; set; }
public string Authors { get; set; }
public string Identifiers { get; set; }
public int Pages { get; set; }
public string ImageUri { get; set; }
}
It seems like there is a problem with mapping Authors property. This Aggregate call will throw an exception if the Authors sequence is null or empty.
.ForMember(x => x.Authors,
opt => opt.MapFrom(src => src.Book.Authors.Select(x => x.Name).Aggregate((i, j) => i + ", " + j)))
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