how do i use AutoMapper in ICollation<> Fields - automapper

Question

when i use AutoMapper for mapping my ViewModels and get All News, thrown error for me.
Errors...
The following property on Mosque.Core.ViewModels.CategoryViewModel cannot be mapped:
Categories
Add a custom mapping expression, ignore, add a custom resolver, or modify the destination type Mosque.Core.ViewModels.CategoryViewModel.
please help me, thank you
//Models
public class News
{
public int Id { get; set; }
public string Title { get; set; }
public virtual ICollection<Category> Categories { get; set; }
public virtual User User { get; set; }
}
public class Category
{
public int Id { get; set; }
public string Title { get; set; }
public virtual ICollection<News> News { get; set; }
}
public class User
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<News> News { get; set; }
}
//ViewModels
public class NewsViewModel
{
public int Id { get; set; }
public string Title { get; set; }
public virtual ICollection<CategoryViewModel> Categories { get; set; }
public virtual UserViewModel User { get; set; }
}
public class CategoryViewModel
{
public int Id { get; set; }
public string Title { get; set; }
public virtual ICollection<NewsViewModel> News { get; set; }
}
public class UserViewModel
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<NewsViewModel> News { get; set; }
}
how do i use for select All News?
--Update1--
I used onion architecture in the project and i installed AutoMapper in the Service layer and i want get all news from repository and fill into ViewModels and pass to the UI.
my code in service layer is...
public List<NewsViewModel> GetAll()
{
Mapper.CreateMap<News, NewsViewModel>()
.ForMember(dest => dest.Categories, src => src.MapFrom(p => p.Categories))
.ForMember(dest => dest.User, src => src.MapFrom(p => p.User));
Mapper.AssertConfigurationIsValid();
var viewModels = new List<NewsViewModel>();
foreach (var item in _newsRepository.GetAll())
{
var viewModel = Mapper.Map<News, NewsViewModel>(item);
viewModels.Add(viewModel);
}
return viewModels;
}

Answer 1

You don't seem to have created maps for Catagory and User.
Add the following maps:
Mapper.CreateMap<User, UserViewModel>();
Mapper.CreateMap<Category, CategoryViewModel>();
By the way, why are you creating the maps inside the GetAll method? You can create the maps once, usually at application startup.