What the best way of translating created user name with ef core 3.1 - ef-core-3.1

Question

public class Entity
{
public string Id { get; set; }
public string CreatedBy { get; set; }
public string LastUpdatedBy { get; set; }
[NotMapped]
public string Creator { get; set; }
[NotMapped]
public string Updater { get; set; }
}
public class User
{
public string Name { get; set; }
public string Id { get; set; }
}
I am going to search Entities, sort on Creator/Updater properties(and return UserInfo.Name) with ef core query, any idea?

Answer 1

After hours of researches, refers
How do you perform a left outer join using linq extension methods
Entity Framework Join 3 Tables
There 3 ways in oder(presonal perfer the first than second):
class Program
{
static void Main()
{
using TenantDBContext dbContext = new TenantDBContext("PORT=5432;DATABASE=linqtosql;HOST=xxx.com;PASSWORD=xxx;USER ID=postgres;Pooling=true;Minimum Pool Size=10;Application Name=xxx");
var result = (
from entity in dbContext.Entities
join user in dbContext.Users on entity.CreatedBy equals user.Id into temp1
from ce in temp1.DefaultIfEmpty()
join user1 in dbContext.Users on entity.UpdatedBy equals user1.Id into temp2
from cu in temp2.DefaultIfEmpty()
select new Entity() { Id = entity.Id, CreatedBy = entity.CreatedBy, UpdatedBy = entity.UpdatedBy, Creator = ce.Name, Updater = ce.Name }
).ToList();
Console.WriteLine(JsonConvert.SerializeObject(result, Formatting.Indented));
var result2 = dbContext.Entities
.GroupJoin(dbContext.Users, e => e.CreatedBy, u => u.Id, (e, u) => new { Entity = e, User = u })
.SelectMany(eUser => eUser.User.DefaultIfEmpty(), (e, u) => new Entity() { Id = e.Entity.Id, CreatedBy = e.Entity.CreatedBy, UpdatedBy = e.Entity.UpdatedBy, Creator = u.Name })
.GroupJoin(dbContext.Users, e => e.UpdatedBy, u => u.Id, (e, u) => new { Entity = e, User = u })
.SelectMany(eUser => eUser.User.DefaultIfEmpty(), (e, u) => new Entity() { Id = e.Entity.Id, CreatedBy = e.Entity.CreatedBy, UpdatedBy = e.Entity.UpdatedBy, Creator = e.Entity.Creator, Updater = u.Name }
).ToList();
Console.WriteLine(JsonConvert.SerializeObject(result2, Formatting.Indented));
var result3 = dbContext.Entities
.SelectMany(entity => dbContext.Users.Where(user => entity.CreatedBy == user.Id).DefaultIfEmpty(), (entity, user) => new { Entity = entity, User = user })
.SelectMany(entity => dbContext.Users.Where(user => entity.Entity.UpdatedBy == user.Id).DefaultIfEmpty(), (entity, user) => new Entity { Id = entity.Entity.Id, CreatedBy = entity.Entity.CreatedBy, UpdatedBy = entity.Entity.UpdatedBy, Creator = entity.User.Name, Updater = user.Name })
.ToList();
Console.WriteLine(JsonConvert.SerializeObject(result2, Formatting.Indented));
}
}