递归模型的 AutoMapper 条件映射

Question

I've got a recursive model class with the following definition:

public class ItemFilterBlockGroup
{
    public ItemFilterBlockGroup(string groupName, ItemFilterBlockGroup parent, bool advanced = false)
    {
        GroupName = groupName;
        ParentGroup = parent;
        Advanced = advanced;
        ChildGroups = new List<ItemFilterBlockGroup>();
    }

    public string GroupName { get; private set; }
    public bool Advanced { get; private set; }
    public ItemFilterBlockGroup ParentGroup { get; private set; }
    public List<ItemFilterBlockGroup> ChildGroups { get; private set; }
}

It has a property called ChildGroups which is a list of itself - this is used to build up a hierarchical model. What I'm trying to do is map this model to view models, but conditionally. Sometimes (depending on a UI setting) I want to include only Child objects with Advanced = false, and sometimes I want to include all models.

Currently I'm achieving this with a nasty hack that involves Mapper.Reset() and runtime re-definition of the maps - this is obviously not good and presents multiple problems:

Mapper.Reset();
if (showAdvanced)
{
    Mapper.CreateMap<ItemFilterBlockGroup, ItemFilterBlockGroupViewModel>();
}
else
{
    Mapper.CreateMap<ItemFilterBlockGroup, ItemFilterBlockGroupViewModel>()
        .ForMember(dest => dest.ChildGroups,
            opts => opts.MapFrom(from => from.ChildGroups.Where(c => c.Advanced == false)));
}

var mappedViewModels = Mapper.Map<ObservableCollection<ItemFilterBlockGroupViewModel>>(blockGroups);

Given an example input hierarchy of models:

Root (Advanced = False)
+-Child 1 (Advanced = True)
+-Child 2 (Advanced = False)
+-Child 3 (Advanced = False)
  +-Child 3 Sub Child 1 (Advanced = False)
  +-Child 3 Sub Child 2 (Advanced = True)

The first CreateMap definition returns this hierarchy untouched, and the second CreateMap definition (with the Advanced parameter) returns this modified hierarchy (all Advanced = true models and their children are excluded from mapping):

Root (Advanced = False)
+-Child 2 (Advanced = False)
+-Child 3 (Advanced = False)
  +-Child 3 Sub Child 1 (Advanced = False)

How can I parameterise the showAdvanced condition and achieve the same result with a single CreateMap definition? I've searched a lot for the right solution, tried ResolveUsing, CustomResolvers, to no avail.

Answer 1

you can use custom converters something like given below , you can customize your mapping setup.

Create a convert class

  internal class AccountConverter : TypeConverter<PD.IAccount, OD.IAccount>
{
    protected override OD.IAccount ConvertCore(PD.IAccount source)
    {
        var result = new Account()
        {
            CustomerNumber = source.CustomerNumber,
            EAccount = source.EAccount,
            EmailAddress = source.EmailAddress
        };

        return result;
    }
}

Then add mapping like this.

Mapper.CreateMap<PD.IAccount, OD.IAccount>()
  .ConvertUsing(new AccountConverter());

Answer 2

You can use context option Items collection to pass values into map function at runtime:

var showAdvanced = true;
var mappedViewModels = Mapper.Map<ObservableCollection<ItemFilterBlockGroupViewModel>>(
    blockGroups, 
    options => options.Items["includeAdvanced"] = showAdvanced);

And use them anywhere where context is available to construct destination object. Within ResolveUsing or ConstructUsing methods for example:

Mapper.CreateMap<ItemFilterBlockGroup, ItemFilterBlockGroupViewModel>()
    .ForMember(destination => destination.ChildGroups, options => options.ResolveUsing(
        (resolution) =>
        {
            var includeAdvanced = (bool)resolution.Context.Options.Items["includeAdvanced"];
            var source = (ItemFilterBlockGroup)resolution.Context.SourceValue;
            if(includeAdvanced)
                return source.ChildGroups;
            else
                return source.ChildGroups.Where(c => c.Advanced == false);               
         }));

If usage of weakly typed dictionary values to pass flag argument look not so pretty to you I suggest to encapsulate this logic within two separated methods, as in Martin Fowler article example.

Answer 3

Well you want to control the logic using a outside parameter that is not part of the object. I bielieve the best way would be to use one mapping, and filter the input object based on your flag. Something like this

 var blockGroupsTemp; if (showAdvanced) blockGroupsTemp = blockGroups; else { blockGroupsTemp = blockGroups.Where(x => x.Advanced == false).ToList(); blockGroupsTemp.ForEach(s => s.ChildGroups.RemoveAll(y => y.Advanced == true)); } var mappedViewModels = Mapper.Map<ObservableCollection<ItemFilterBlockGroupViewModel>>(blockGroupsTemp);