C#用表达式树实现深拷贝功能

因为对表达式树有点兴趣，出于练手的目的，试着写了一个深拷贝的工具库。支持.net standard2.0或.net framework4.5及以上。

GitHub地址https://github.com/blurhkh/DeepCopier

nuget地址https://www.nuget.org/packages/DeepCopier

使用方法如下：.

首先创建几个测试用的类型

public class Author    {        public string Name { get; set; }    }
    public class Book    {        public string Title { get; set; }        public Author Author { get; set; }        public List<string> Tags { get; set; }    }
    public class BookDTO    {        public string Title { get; set; }        public Author Author { get; set; }        public List<string> Tags { get; set; }    }

Book book = new Book        {            Author = new Author { Name = "Author" },            Title = "Title",            Tags = new List<string> { "dotnet-core", "c#" }        };
        // 用法1 深拷贝一个对象        Book book2 = Copier.Copy(book);        // 或一个IEnumerable<T>的实现类实例（目前仅支持一维数组和ICollection<T>的实现类）        HashSet<Book> books = new HashSet<Book>() { book, book };        HashSet<Book> books2 = Copier.Copy(books);
        // 用法2 新建目标类型实例，并将源对象的属性值拷贝至目标对象的对应属性        BookDTO bookDTO = Copier.Copy<Book, BookDTO>(book);
        // 用法3 将源对象的属性值拷贝至已存在的目标对象的对应属性        BookDTO target = new BookDTO();        Copier.Copy(book, target);

同类的工具库比如较为常见的AutoMapper和一个Reflection.Emit操作IL写的DeepCopy（https://www.nuget.org/packages/DeepCopy/）

接下来进行一下和他们的性能对比，测试数据采用上面的Book类型，循环次数为100万次。

测试数据如下：

Book book = new Book        {            Author = new Author { Name = "Author" },            Title = "Title",            Tags = new List<string> { "dotnet-core", "c#" }        };

测试内容如下（本人PC的CPU为I7 4790k，不同库的测试代码分别跑在不同的程序里）：

首先和AutoMapper进行对比

BookDTO bookDTO = null;
Stopwatch sw = new Stopwatch();sw.Start();for (int i = 0; i < 1000000; i++){    bookDTO = DeepCopier.Copier.Copy<Book, BookDTO>(book);}Console.WriteLine($"DeepCopier costed {sw.ElapsedMilliseconds} ms at 1st time.");
sw.Restart();
for (int i = 0; i < 1000000; i++){    bookDTO = DeepCopier.Copier.Copy<Book, BookDTO>(book);}// 因为有了前一次的缓存，这里速度会更快Console.WriteLine($"DeepCopier costed {sw.ElapsedMilliseconds} ms at 2nd time.");Console.ReadLine();

C#用表达式树实现深拷贝功能

// AutoMapper需要提前配置            AutoMapper.Mapper.Initialize(config => {                config.CreateMap<Book, BookDTO>();            });
            BookDTO bookDTO = null;
            Stopwatch sw = new Stopwatch();            sw.Start();            for (int i = 0; i < 1000000; i++)            {                bookDTO = AutoMapper.Mapper.Map<Book, BookDTO>(book);            }            Console.WriteLine($"AutoMapper costed {sw.ElapsedMilliseconds} ms at 1st time.");
            sw.Restart();
            for (int i = 0; i < 1000000; i++)            {                bookDTO = AutoMapper.Mapper.Map<Book, BookDTO>(book);            }            Console.WriteLine($"AutoMapper costed {sw.ElapsedMilliseconds} ms at 2nd time.");            Console.ReadLine();

C#用表达式树实现深拷贝功能

// DeepCopy只支持对自身类型的拷贝            Book temp = null;
            Stopwatch sw = new Stopwatch();            sw.Start();            for (int i = 0; i < 1000000; i++)            {                temp = DeepCopy.DeepCopier.Copy(book);            }            Console.WriteLine($"DeepCopy costed {sw.ElapsedMilliseconds} ms at 1st time.");
            sw.Restart();
            for (int i = 0; i < 1000000; i++)            {                temp = DeepCopy.DeepCopier.Copy(book);            }            Console.WriteLine($"DeepCopy costed {sw.ElapsedMilliseconds} ms at 2nd time.");            Console.ReadLine();

C#用表达式树实现深拷贝功能

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