Can Automapper map a paged list?

Question

I\'d like to map a paged list of business objects to a paged list of view model objects using something like this:

var listViewModel = _mappingEngine.Map

        

Answer 1

AutoMapper automatically handles conversions between several types of lists and arrays: http://automapper.codeplex.com/wikipage?title=Lists%20and%20Arrays

It doesn't appear to automatically convert custom types of lists inherited from IList, but a work around could be:

    var pagedListOfRequestForQuote = new PagedList<RequestForQuoteViewModel>(
        AutoMapper.Mapper.Map<List<RequestForQuote>, List<RequestForQuoteViewModel>>(((List<RequestForQuote>)requestForQuotes),
        page ?? 1,
        pageSize

Answer 2

I created a little wrapper around AutoMapper to map PagedList<DomainModel> to PagedList<ViewModel>.

public class MappingService : IMappingService
{
    public static Func<object, Type, Type, object> AutoMap = (a, b, c) =>
    {
        throw new InvalidOperationException(
            "The Mapping function must be set on the MappingService class");
    };

    public PagedList<TDestinationElement> MapToViewModelPagedList<TSourceElement, TDestinationElement>(PagedList<TSourceElement> model)
    {
        var mappedList = MapPagedListElements<TSourceElement, TDestinationElement>(model);
        var index = model.PagerInfo.PageIndex;
        var pageSize = model.PagerInfo.PageSize;
        var totalCount = model.PagerInfo.TotalCount;

        return new PagedList<TDestinationElement>(mappedList, index, pageSize, totalCount);
    }

    public object Map<TSource, TDestination>(TSource model)
    {
        return AutoMap(model, typeof(TSource), typeof(TDestination));
    }

    public object Map(object source, Type sourceType, Type destinationType)
    {
        if (source is IPagedList)
        {
            throw new NotSupportedException(
                "Parameter source of type IPagedList is not supported. Please use MapToViewModelPagedList instead");
        }

        if (source is IEnumerable)
        {
            IEnumerable<object> input = ((IEnumerable)source).OfType<object>();
            Array a = Array.CreateInstance(destinationType.GetElementType(), input.Count());

            int index = 0;
            foreach (object data in input)
            {
                a.SetValue(AutoMap(data, data.GetType(), destinationType.GetElementType()), index);
                index++;
            }
            return a;
        }

        return AutoMap(source, sourceType, destinationType);
    }

    private static IEnumerable<TDestinationElement> MapPagedListElements<TSourceElement, TDestinationElement>(IEnumerable<TSourceElement> model)
    {
        return model.Select(element => AutoMap(element, typeof(TSourceElement), typeof(TDestinationElement))).OfType<TDestinationElement>();
    }
}

Usage:

PagedList<Article> pagedlist = repository.GetPagedList(page, pageSize);
mappingService.MapToViewModelPagedList<Article, ArticleViewModel>(pagedList);

It is important that you would have to use the element types!

If you have any question or suggestions, please feel free to comment :)

Answer 3

Using jrummell's answer, I created an extension method that works with Troy Goode's PagedList. It keeps you from having to put so much code everywhere...

    public static IPagedList<TDestination> ToMappedPagedList<TSource, TDestination>(this IPagedList<TSource> list)
    {
        IEnumerable<TDestination> sourceList = Mapper.Map<IEnumerable<TSource>, IEnumerable<TDestination>>(list);
        IPagedList<TDestination> pagedResult = new StaticPagedList<TDestination>(sourceList, list.GetMetaData());
        return pagedResult;

    }

Usage is:

var pagedDepartments = database.Departments.OrderBy(orderBy).ToPagedList(pageNumber, pageSize).ToMappedPagedList<Department, DepartmentViewModel>();

Answer 4

If you're using Troy Goode's PageList, there's a StaticPagedList class that can help you map.

// get your original paged list
IPagedList<Foo> pagedFoos = _repository.GetFoos(pageNumber, pageSize);
// map to IEnumerable
IEnumerable<Bar> bars = Mapper.Map<IEnumerable<Bar>>(pagedFoos);
// create an instance of StaticPagedList with the mapped IEnumerable and original IPagedList metadata
IPagedList<Bar> pagedBars = new StaticPagedList<Bar>(bars, pagedFoos.GetMetaData());

Answer 5

I needed to return a serializable version of IPagedList<> with AutoMapper version 6.0.2 that supports the IMapper interface for ASP.NET Web API. So, if the question was how do I support the following:

//Mapping from an enumerable of "foo" to a different enumerable of "bar"...
var listViewModel = _mappingEngine.Map<IPagedList<RequestForQuote>, PagedViewModel<RequestForQuoteViewModel>>(requestForQuotes);

Then one could do this:

Define PagedViewModel<T>
Source: AutoMapper Custom Type Converter not working

public class PagedViewModel<T>
{
    public int FirstItemOnPage { get; set; }
    public bool HasNextPage { get; set; }
    public bool HasPreviousPage { get; set; }
    public bool IsFirstPage { get; set; }
    public bool IsLastPage { get; set; }
    public int LastItemOnPage { get; set; }
    public int PageCount { get; set; }
    public int PageNumber { get; set; }
    public int PageSize { get; set; }
    public int TotalItemCount { get; set; }
    public IEnumerable<T> Subset { get; set; }
}

Write open generic converter from IPagedList<T> to PagedViewModel<T>
Source: https://github.com/AutoMapper/AutoMapper/wiki/Open-Generics

public class Converter<TSource, TDestination> : ITypeConverter<IPagedList<TSource>, PagedViewModel<TDestination>>
{
    public PagedViewModel<TDestination> Convert(IPagedList<TSource> source, PagedViewModel<TDestination> destination, ResolutionContext context)
    {
        return new PagedViewModel<TDestination>()
        {
            FirstItemOnPage = source.FirstItemOnPage,
            HasNextPage = source.HasNextPage,
            HasPreviousPage = source.HasPreviousPage,
            IsFirstPage = source.IsFirstPage,
            IsLastPage = source.IsLastPage,
            LastItemOnPage = source.LastItemOnPage,
            PageCount = source.PageCount,
            PageNumber = source.PageNumber,
            PageSize = source.PageSize,
            TotalItemCount = source.TotalItemCount,
            Subset = context.Mapper.Map<IEnumerable<TSource>, IEnumerable<TDestination>>(source) //User mapper to go from "foo" to "bar"
        };
    }
}

Configure mapper

new MapperConfiguration(cfg =>
    {
        cfg.CreateMap<RequestForQuote, RequestForQuoteViewModel>();//Define each object you need to map
        cfg.CreateMap(typeof(IPagedList<>), typeof(PagedViewModel<>)).ConvertUsing(typeof(Converter<,>)); //Define open generic mapping
    });

Answer 6

AutoMapper does not support this out of the box, as it doesn't know about any implementation of IPagedList<>. You do however have a couple of options:

1. Write a custom IObjectMapper, using the existing Array/EnumerableMappers as a guide. This is the way I would go personally.

2. Write a custom TypeConverter, using:

   Mapper
       .CreateMap<IPagedList<Foo>, IPagedList<Bar>>()
       .ConvertUsing<MyCustomTypeConverter>();
   

   and inside use Mapper.Map to map each element of the list.