Automapper用子对象覆盖丢失的源属性列表

Question

我遇到了Automapper问题。我建立了一个测试窗体表单应用程序，下面是代码。也看看每个MessageBox后的意见：

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!! 

     } 
    } 

我该怎么做才能避免这种情况？预期这种行为？ 无论如何，任何人都可以指导我如何使SecondClass孩子SecondChildProp保持“SecondClass”，因为它是在映射发生之前。

Answer 1

我问了一个类似的问题here，发现另一个类似的问题here。

我认为@PatrickSteele提出了一个很好的观点：AutoMapper应该如何将源列表映射到现有对象的目标列表，当dest列表可能不一定与源列表有任何相似之处？即“But what if one list has 3 and the other list has 5?”

如果你确信FirstClass和SecondClass有相同数量的Children和如果的FirstClass的第n个子总是对应于SecondClass的第N个孩子，你可以尝试这样的事情：

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是某种独特的键：

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); 
      } 
     });