AutoMapper展平嵌套的集合 [英] AutoMapper flatten nested collections

问题描述

我试图弄清楚如何将商户集合展平，每个商户都将订单集合包含到平坦的OrderViewModels列表中.

I try to figure out how to flatten a collection of Merchants, each containing a collection of Orders to a flat List of OrderViewModels.

这是我的DTO:

public class Merchant
{
    public string MerchantName { get; set; }
    public List<Order> Orders { get; set; }
}

public class Order
{
    public string OrderId { get; set; }
}

这是视图模型:

public class OrderViewModel
{
    public string MerchantName { get; set; }
    public string OrderId { get; set; }
}

我的目标是将列表< Merchant> 展平为 List< OrderViewModel> ，而以下测试结构应生成6个视图模型:

My Goal is to flatten a List<Merchant> to a List<OrderViewModel> whereas the following test structure should result in 6 view models:

var myMerchants = new List<Merchant>
{
    new Merchant
    {
        MerchantName = "Merchant X",
        Orders = new List<Order>
        {
             new Order { OrderId = "Order 1"},
             new Order { OrderId = "Order 2"},
             new Order { OrderId = "Order 3"}
        }
    },
    new Merchant
    {
        MerchantName = "Merchant Y",
        Orders = new List<Order>
        {
            new Order { OrderId = "Order 4"},
            new Order { OrderId = "Order 5"},
            new Order { OrderId = "Order 6"}
        }
    }
 };

 var models = Mapper.Map<List<OrderViewModel>>(myMerchants);

推荐答案

由于根对象的基数不是1:1，(即2个根Merchants需要映射到6个OrderViewModels)，您可以需要诉诸自定义TypeConverter 并在收集级别进行操作，您可以在其中使用.SelectMany进行展平:

Because the cardinality of the root objects isn't 1:1, (i.e. 2 root Merchants need to map to 6 OrderViewModels), you may need to resort to a custom TypeConverter and operate at the collection level, where you can use .SelectMany to do the flattening:

public class MyTypeConverter : ITypeConverter<IEnumerable<Merchant>, List<OrderViewModel>>
{
    public List<OrderViewModel> Convert(ResolutionContext context)
    {
        if (context == null || context.IsSourceValueNull)
            return null;

        var source = context.SourceValue as IEnumerable<Merchant>;

        return source
            .SelectMany(s => s.Orders
              .Select(o => new OrderViewModel
              {
                  MerchantName = s.MerchantName,
                  OrderId = o.OrderId
              }))
              .ToList();
    }
}

然后您可以进行引导:

Mapper.CreateMap<IEnumerable<Merchant>, List<OrderViewModel>>()
    .ConvertUsing<MyTypeConverter>();

然后这样映射:

var models = Mapper.Map<List<OrderViewModel>>(myMerchants);

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