试试automapper

用nuget安装AutoMapper。
如果熟悉相同，可以直接mapper；如果不同，就需要定义下mapper规则，这里先展示个简单的用法。

一些类：

 public class Book
{
    public string Title { get; set; }
    public Author Author { get; set; }
    public Prd product { get; set; }
}
public class BookViewModel
{
    public string Title { get; set; }
    public string Author { get; set; }
    public string ItemNo { get; set; }
}
public class Author
{
    public string Name { get; set; }
}
public class Prd
{
    public string itemNo { get; set; }
    public string model { get; set; }
}

使用：

    static void Main(string[] args)
    {
        //方式1：
        var a = new AutoMapper.Configuration.MapperConfigurationExpression();

        a.CreateMap<Book, Author>().ForMember(dest => dest.Name,
            opts => opts.MapFrom(src => src.Author.Name));

        a.CreateMap<Book, BookViewModel>().ForMember(dest => dest.ItemNo,
           opts => opts.MapFrom(src => src.product.itemNo))
            .ForMember(dest => dest.Author,
            opts => opts.MapFrom(src => src.Author.Name));

        AutoMapper.Mapper.Initialize(a);

        //方式2：
        //AutoMapper.Mapper.Initialize(c => {
        //    c.CreateMap<Book, BookViewModel>().ForMember(dest => dest.Author,
        //    opts => opts.MapFrom(src => src.Author.Name));

        //    c.CreateMap<Book, Author>().ForMember(dest => dest.Name,
        //    opts => opts.MapFrom(src => src.Author.Name));
        //});

        Book b1 = new Book();
        b1.Title = "题目";
        b1.Author = new Author();
        b1.Author.Name = "作者";
        b1.product = new Prd();
        b1.product.itemNo = "12001";
        b1.product.model = "a3001";

        BookViewModel bvm = AutoMapper.Mapper.Map<BookViewModel>(b1);
        Console.WriteLine(JsonHelper.ToJson(bvm));

        Author author = AutoMapper.Mapper.Map<Author>(b1);
        Console.WriteLine(JsonHelper.ToJson(author));

        Console.ReadKey();
    }

结果：

image.png