AutoMapper忽略复杂类型的父属性

Question

我正在使用AutoMapper 6.2.2，我有一个通用方法，可以执行从一种类型到另一种类型的对象图更新。我不知道运行时的所有组合，因为mapper包含在扩展方法中，该方法使用T作为CreateMap类型参数。

我已完成配置，但问题是，Foo.MyBar已更新，而不是降序并比较其子属性。如果它为null，我只希望Foo.MyBar被完全覆盖。由于我无法专门为Foo.MyBar进行配置，如何在我的配置中编写通用条件来满足我的需求？

我期待result.MyBar.TwoString =＆＃34; yyy＆＃34;，而不是＆＃34;世界＆＃34;。

public class Bar
{
    public string OneString { get; set; }

    [ReadOnly(true)]
    public string TwoString { get; set; }
}

public class Foo
{
    public Bar MyBar { get; set; }

    public int? MyNumber { get; set; }

    [ReadOnly(true)]
    public string MyString { get; set; }

    public string[] MyStringArray { get; set; }
}

internal class Program
{
    private static void Main()
    {
        Foo model = new Foo
        {
            MyString = "aaa",
            MyNumber = 42,
            MyBar = new Bar { OneString = "xxx", TwoString = "yyy" }
        };

        Foo update = new Foo
        {
            MyString = "bbb",
            MyNumber = 77,
            MyBar = new Bar { OneString = "hello", TwoString = "world" }
        };

        MapperConfiguration config = new MapperConfiguration(cfg =>
        {
            cfg.AllowNullCollections = true;
            cfg.CreateMissingTypeMaps = true;
            cfg.CreateMap<Foo, Foo>();
            cfg.CreateMap<Foo, Foo>().ForAllMembers(opt =>
                opt.Condition((source, destination, sourceMember, destMember) =>
                    (sourceMember != null)));
            cfg.ForAllPropertyMaps(map =>
                    map.SourceMember.GetCustomAttribute<ReadOnlyAttribute>()?.IsReadOnly == true,
                (map, configuration) =>
                {
                    configuration.Ignore();
                });
        });

        var mapper = config.CreateMapper();

        Foo result = mapper.Map(update, model);
    }
}