Automapper用子對象覆蓋丟失的源屬性列表

Question

我遇到了Automapper問題。我建立了一個測試窗體表單應用程序，下面是代碼。也看看每個MessageBox後的意見：

public class FirstClass 
    { 
     public string FirstProp { get; set; } 
     public IList<FirstClassChild> Children { get; set; } 
    } 

    public class FirstClassChild 
    { 
     public string FirstChildProp { get; set; } 
    } 

    public class SecondClass 
    { 
     public string FirstProp { get; set; } 
     public string SecondProp { get; set; } 
     public IList<SecondClassChild> Children { get; set; } 
    } 

    public class SecondClassChild 
    { 
     public string FirstChildProp { get; set; } 
     public string SecondChildProp { get; set; } 
    } 

    public partial class Form1 : Form 
    { 
     public Form1() 
     { 
      InitializeComponent(); 

      AutoMapper.Mapper.CreateMap<FirstClass, SecondClass>(); 
      AutoMapper.Mapper.CreateMap<FirstClassChild, SecondClassChild>(); 

      var f = new FirstClass { FirstProp = "FirstClass" }; 
      f.Children = new List<FirstClassChild> { new FirstClassChild { FirstChildProp = "FirstClass" } }; 
      var s = new SecondClass { FirstProp = "SecondClass", SecondProp = "SecondClass" }; 
      s.Children = new List<SecondClassChild> { new SecondClassChild { FirstChildProp = "SecondClass", SecondChildProp = "SecondClass" } }; 
      AutoMapper.Mapper.Map(f, s); 

      var fc = new FirstClassChild { FirstChildProp = "FirstClass" }; 
      var sc = new SecondClassChild { FirstChildProp = "SecondClass", SecondChildProp = "SecondClass" }; 
      AutoMapper.Mapper.Map(fc, sc); 

      MessageBox.Show(sc.FirstChildProp);//FirstClass as expected 
      MessageBox.Show(sc.SecondChildProp);//SecondClass as expected 

      MessageBox.Show(s.FirstProp);//FirstClass as expected 
      MessageBox.Show(s.SecondProp);//SecondClass as expected 
      MessageBox.Show(s.Children.First().FirstChildProp);//FirstClass as expected 
      MessageBox.Show(s.Children.First().SecondChildProp);//Empty not expected!! 

     } 
    } 

我該怎麼做才能避免這種情況？預期這種行爲？ 無論如何，任何人都可以指導我如何使SecondClass孩子SecondChildProp保持「SecondClass」，因爲它是在映射發生之前。

Answer 1

我問了一個類似的問題here，發現另一個類似的問題here。

我認爲@PatrickSteele提出了一個很好的觀點：AutoMapper應該如何將源列表映射到現有對象的目標列表，當dest列表可能不一定與源列表有任何相似之處？即「But what if one list has 3 and the other list has 5?」

如果你確信FirstClass和SecondClass有相同數量的Children和如果的FirstClass的第n個子總是對應於SecondClass的第N個孩子，你可以嘗試這樣的事情：

Mapper.CreateMap<FirstClass, SecondClass>() 
    .ForMember(m => m.Children, o => o.Ignore()) 
    .AfterMap((src, dest) => 
     { 
      for (var i = 0; i < dest.Children.Count; i++) 
       Mapper.Map(src.Children[i], dest.Children[i]); 
     }); 

，或者如果FirstChildProp是某種獨特的鍵：

Mapper.CreateMap<FirstClass, SecondClass>() 
    .ForMember(m => m.Children, o => o.Ignore()) 
    .AfterMap((src, dest) => 
     { 
      foreach (var dChild in dest.Children) 
      { 
       var sChild = src.Children.Single(c => c.FirstChildProp == dChild.FirstChildProp); 
       Mapper.Map(sChild, dChild); 
      } 
     });