Fastest Way to do Shallow Copy in C#

Question

I wonder what is the fastest way to do shallow copying in C#? I only know there are 2 ways to do shallow copy:

1. MemberwiseClone
2. Copy each field one by

Answer 1

In fact, MemberwiseClone is usually much better than others, especially for complex type.

The reason is that:if you manual create a copy, it must call one of the type's constructor, but use memberwise clone, I guess it just copy a block of memory. for those types has very expensive construct actions, memberwise clone is absolutely the best way.

Onece i wrote such type: {string A = Guid.NewGuid().ToString()}, I found memberwise clone is muct faster than create a new instance and manual assign members.

The code below's result:

Manual Copy:00:00:00.0017099

MemberwiseClone:00:00:00.0009911

namespace MoeCard.TestConsole
{
    class Program
    {
        static void Main(string[] args)
        {
            Program p = new Program() { AAA = Guid.NewGuid().ToString(), BBB = 123 };
            Stopwatch sw = Stopwatch.StartNew();
            for (int i = 0; i < 10000; i++)
            {
                p.Copy1();
            }
            sw.Stop();
            Console.WriteLine("Manual Copy:" + sw.Elapsed);

            sw.Restart();
            for (int i = 0; i < 10000; i++)
            {
                p.Copy2();
            }
            sw.Stop();
            Console.WriteLine("MemberwiseClone:" + sw.Elapsed);
            Console.ReadLine();
        }

        public string AAA;

        public int BBB;

        public Class1 CCC = new Class1();

        public Program Copy1()
        {
            return new Program() { AAA = AAA, BBB = BBB, CCC = CCC };
        }
        public Program Copy2()
        {
            return this.MemberwiseClone() as Program;
        }

        public class Class1
        {
            public DateTime Date = DateTime.Now;
        }
    }

}

finally, I provide my code here:

    #region 数据克隆
    /// 

    /// 依据不同类型所存储的克隆句柄集合
    /// 
    private static readonly Dictionary> CloneHandlers = new Dictionary>();

    /// 

    /// 根据指定的实例,克隆一份新的实例
    /// 
    /// 待克隆的实例
    /// 被克隆的新的实例
    public static object CloneInstance(object source)
    {
        if (source == null)
        {
            return null;
        }
        Func handler = TryGetOrAdd(CloneHandlers, source.GetType(), CreateCloneHandler);
        return handler(source);
    }

    /// 

    /// 根据指定的类型,创建对应的克隆句柄
    /// 
    /// 数据类型
    /// 数据克隆句柄
    private static Func CreateCloneHandler(Type type)
    {
        return Delegate.CreateDelegate(typeof(Func), new Func(CloneAs