using System;

using System.Collections.Generic;

using System.Linq;

using System.Reflection;

​

// source: https://github.com/jhewlett/ValueObject

[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field)]

internal sealed class IgnoreMemberAttribute : Attribute

{ }

​

internal interface IValueObject<T>

    : IEquatable<T>

{

    public int GetHashCode();

​

    public int HashValue(int seed, object value);

}

​

// Learn more: https://docs.microsoft.com/en-us/dotnet/standard/microservices-architecture/microservice-ddd-cqrs-patterns/implement-value-objects

// source: https://github.com/jhewlett/ValueObject

public abstract class ValueObject : IValueObject<ValueObject>

{

    private List<FieldInfo>? _fields;

​

    private List<PropertyInfo>? _properties;

​

    #region IValueObject<ValueObject> Members

​

    public override int GetHashCode()

    {

        var hash = GetProperties()

           .Select(property => property.GetValue(this, null))

           .Aggregate(17, HashValue);

​

        return GetFields()

           .Select(field => field.GetValue(this))

           .Aggregate(hash, HashValue);

    }

​

    public int HashValue(int seed, object? value)

    {

        var currentHash = value?.GetHashCode() ?? 0;

​

        return seed * 23 + currentHash;

    }

​

    public virtual bool Equals(ValueObject? other) => Equals(other as object);

​

    #endregion

​

    public static bool operator ==(ValueObject? left, ValueObject? right)

    {

        if (left is null ^ right is null) return false;

​

        return left?.Equals(right) != false;

    }

​

    public static bool operator !=(ValueObject? left, ValueObject? right) => !(left == right);

​

    public override bool Equals(object? obj)

    {

        if (obj           == null

         || obj.GetType() != GetType()) return false;

​

        return GetProperties().All(p => PropertiesAreEqual(obj, p))

            && GetFields().All(f => FieldsAreEqual(obj, f));

    }

​

    private bool PropertiesAreEqual(object obj, PropertyInfo p) =>

        Equals(p.GetValue(this, null), p.GetValue(obj, null));

​

    private bool FieldsAreEqual(object obj, FieldInfo f) => Equals(f.GetValue(this), f.GetValue(obj));

​

    private IEnumerable<PropertyInfo> GetProperties()

    {

        return _properties ??= GetType()

           .GetProperties(BindingFlags.Instance | BindingFlags.Public)

           .Where(p => p.GetCustomAttribute(typeof(IgnoreMemberAttribute)) is null)

           .ToList();

    }

​

    private IEnumerable<FieldInfo> GetFields()

    {

        return _fields ??= GetType()

           .GetFields(BindingFlags.Instance | BindingFlags.Public)

           .Where(f => f.GetCustomAttribute(typeof(IgnoreMemberAttribute)) is null)

           .ToList();

    }

}

​

public sealed class FullNameVo : ValueObject

{

    public FullNameVo(string name, string surname)

    {

        Name    = name;

        Surname = surname;

    }

​

    [IgnoreMember]

    public string Name { get; }

​

    public string Surname { get; }

​

    [IgnoreMember]

    public string FullName => $"{Name} {Surname}";

}

​

internal class Program

{

    private static void Main(string[] args)

    {

        var user1 = new FullNameVo("John", "Doe");

        var user2 = new FullNameVo("John", "Doe");

        var user3 = new FullNameVo("Jane", "Doe");

​

        Console.WriteLine(user1 == user2); // True

        Console.WriteLine(ReferenceEquals(user1, user2)); // False

        Console.WriteLine(user1 == user3); // True

        Console.WriteLine(user1.Equals(user3)); // True

    }

}