using System;

using System.Text.Json;

using System.Collections.Generic;

using System.Linq.Expressions;

using System.Reflection;

​

class Person

{

    public int Id { get; set; }

    public string Phone { get; set; }

    public string Name { get; set; }

    public static Expression<Func<Person, object>>[] SelectAll(){

        return new Expression<Func<Person, object>>[]{ x=>x.Id, x=>x.Phone, x=>x.Name};

    }

}

​

class Program

{

    static void Main(string[] args)

    {

        var personReceiveValues = new Person { Id=1, Phone = "1111111111", Name="A" };

        var personNewValues = new Person { Id=0, Phone = "3333333333", Name="C" };

        Console.WriteLine(JsonSerializer.Serialize(personReceiveValues));

        UpdateObj<Person>(personReceiveValues, personNewValues, x => x.Phone);

        Console.WriteLine(JsonSerializer.Serialize(personNewValues));

        Console.WriteLine(JsonSerializer.Serialize(personReceiveValues));

        Console.WriteLine("---------------");

        personReceiveValues = new Person { Id=1, Phone = "1111111111", Name="A" };

        personNewValues = new Person { Id=0, Phone = "3333333333", Name="C" };

        Console.WriteLine(JsonSerializer.Serialize(personReceiveValues));

        UpdateObj<Person>(personReceiveValues, personNewValues, x => x.Phone,x=>x.Name);

        Console.WriteLine(JsonSerializer.Serialize(personNewValues));

        Console.WriteLine(JsonSerializer.Serialize(personReceiveValues));

        Console.WriteLine("---------------");

        personReceiveValues = new Person { Id=1, Phone = "1111111111", Name="A" };

        personNewValues = new Person { Id=0, Phone = "3333333333", Name="C" };

        Console.WriteLine(JsonSerializer.Serialize(personReceiveValues));

        var a = Person.SelectAll();

        UpdateObj<Person>(personReceiveValues, personNewValues, a);

        Console.WriteLine(JsonSerializer.Serialize(personNewValues));

        Console.WriteLine(JsonSerializer.Serialize(personReceiveValues));

        Console.WriteLine("---------------");

        var runTimes = 20000;

        var watch = System.Diagnostics.Stopwatch.StartNew();

        for(int i =0;i<runTimes;i++){

            personReceiveValues = new Person { Id=1, Phone = "1111111111", Name="A" };

            personNewValues = new Person { Id=0, Phone = "3333333333", Name="C" };

            UpdateObj<Person>(personReceiveValues, personNewValues, x => x.Phone,x=>x.Name);

        }

        watch.Stop();

        float elapsed1 = watch.ElapsedMilliseconds;

        Console.WriteLine("run time 1: "+elapsed1);

        watch = System.Diagnostics.Stopwatch.StartNew();

        for(int i =0;i<runTimes;i++){

            personReceiveValues = new Person { Id=1, Phone = "1111111111", Name="A" };

            personNewValues = new Person { Id=0, Phone = "3333333333", Name="C" };

            UpdateObj<Person>(personReceiveValues, personNewValues, x => x.Phone,x=>x.Name);

            personReceiveValues.Name = personNewValues.Name;

            personReceiveValues.Phone = personNewValues.Phone;

        }

        watch.Stop();

        float elapsed2 = watch.ElapsedMilliseconds;

        Console.WriteLine("run time 2: "+elapsed2);

        float deltaElpased = elapsed1 - elapsed2;

        Console.WriteLine("diff: "+deltaElpased);

        Console.WriteLine(((deltaElpased/elapsed2)*100)+"%");

    }

​

    static void UpdateObj<T>(T objToUpdate, T objWithValues, params Expression<Func<T, object>>[] selectors)

    {

        var properties = new List<Expression<Func<T, object>>>();

        foreach(var selector in selectors){

            var memberInitExpression = selector.Body as MemberExpression;

            while (memberInitExpression != null)

            {

                properties.Add(Expression.Lambda<Func<T, object>>(memberInitExpression, selector.Parameters));

                memberInitExpression = memberInitExpression.Expression as MemberExpression;

            }

        }

​

        properties.Reverse();

        foreach (var fieldSelector in properties)

        {

            if (fieldSelector.Body is MemberExpression memberExpression)

            {

                if (memberExpression.Member is PropertyInfo property)

                {

                    var newValue = fieldSelector.Compile()(objWithValues);

                    property.SetValue(objToUpdate, newValue);

                }

            }

        }

    }

}

​

​