ContactEdit.cs

namespace ContactList.Features.Contact
{
    using System;
    using AutoMapper;
    using ContactLists.Core;
    using Core.Domain;
    using FluentValidation;
    using MediatR;

    public class ContactEdit
    {
        public class Query : IRequest<Command>
        {
            public Guid Id { get; set; }
        }

        public class QueryHandler : IRequestHandler<Query, Command>
        {
            private readonly ContactsContext _database;

            public QueryHandler(ContactsContext database)
            {
                _database = database;
            }

            public Command Handle(Query message)
            {
                var contact = _database.Contacts.Find(message.Id);

                return Mapper.Map<Contact, Command>(contact);
            }
        }

        public class Command : IRequest
        {
            public Guid Id { get; set; }

            public string Name { get; set; }
            public string Email { get; set; }
            public string Phone { get; set; }
        }

        public class Validator : AbstractValidator<Command>
        {
            public Validator()
            {
                RuleFor(x => x.Name).NotEmpty();
                RuleFor(x => x.Email).EmailAddress();

                RuleFor(x => x.Name).Length(1, 255);
                RuleFor(x => x.Email).Length(1, 255);
                RuleFor(x => x.Phone).Length(1, 50);
            }
        }

        public class CommandHandler : RequestHandler<Command>
        {
            private readonly ContactsContext _database;

            public CommandHandler(ContactsContext database)
            {
                _database = database;
            }

            protected override void HandleCore(Command message)
            {
                var contact = _database.Contacts.Find(message.Id);

                Mapper.Map(message, contact);
            }
        }
    }
}