c# - 如果 Not Null，则 AutoMapper 映射嵌套对象的属性

Question

我有以下示例对象..

  public class ComplexObject
  {
    public string Name { get; set; }
    public SimpleObject Child1 { get; set; }
    public SimpleObject Child2 { get; set; }
  }
  public class SimpleObject : IEquatable< SimpleObject >
  {
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Gender { get; set; }
    public int? Age { get; set; }
  }

使用以下 AutoMapper 配置

  Mapper.CreateMap<SimpleObject, SimpleObject>()
    .ForAllMembers(expression=>expression.Condition(r=>!r.IsSourceValueNull));

  Mapper.CreateMap<ComplexObject, ComplexObject>()
    .ForAllMembers(expression=>expression.Condition(resolutionContext=>!resolutionContext.IsSourceValueNull));

和下面的 NUnit 测试...

[SetUp] public void Should_run_before_each_test()
{
  child1 = new SimpleObject { FirstName = "Tom", LastName = "Smith", Age = 34, Gender = "Male" };
  child2 = new SimpleObject { FirstName = "Andy", LastName = "Smith-bob", Age = 21, Gender = "Male" };
}

[ Test ]
public void Should_ignore_null_properties_in_nested_objects()
{
  var source = new ComplexObject()
  {
    Name = "blue",
    Child1 = new SimpleObject{FirstName = "dot", LastName = "net"}
  };
  var destination = new ComplexObject()
  {
    Name = "Andy",
    Child1 = child1,
    Child2 = child2
  };

  destination = Mapper.Map(source, destination);

  destination.Name.Should(Be.EqualTo(source.Name));
  destination.Child1.FirstName.Should(Be.EqualTo("dot"));
  destination.Child1.LastName.Should(Be.EqualTo("net")  );
  destination.Child1.Age.Should(Be.EqualTo(child1.Age)  );
  destination.Child1.Gender.Should(Be.EqualTo(child1.Gender)  );
}

当 AutoMapper 将 null 推送到目标对象时断言年龄时，上述测试失败。

我是对 AutoMapper 期望过高，还是错过了一些重要的 map 配置步骤。

最终目标是通过 MVC 操作将非常复杂的域对象绑定(bind)到传入的表单数据。然后，AutoMapper 将用于仅将非空属性(在对象图的所有深度)合并到在整个多步骤表单中维护的真实实例中。

以防万一有人需要知道......我也尝试了以下映射配置但没有任何运气:(

  Mapper.CreateMap<ComplexObject, ComplexObject>()
    .ForMember(x=>x.Child1, l=>l.ResolveUsing(x=>x.Child1 == null?null:Mapper.Map<SimpleObject,SimpleObject>(x.Child1)))
    .ForMember(x=>x.Child2, l=>l.ResolveUsing(x=>x.Child2 == null?null:Mapper.Map<SimpleObject,SimpleObject>(x.Child2)))
    .ForAllMembers(expression=>expression.Condition(resolutionContext=>!resolutionContext.IsSourceValueNull));

Answer 1

如果源值为空，为什么你期望目标对象的值不为空？ int? 的默认值为 null，因此，当您调用

destination.Child1.Age.Should(Be.EqualTo(child1.Age));

.Should 失败了。这应该是预期的行为。

尝试类似 Assert.Null(detination.Child1.Age) 的操作，它应该会通过。 AutoMapper 不会“推送”值，没有源值，因此，Age 只会使用默认值。