FiltruCompus.cs

static void Main()
{
	Mapper.Initialize(cfg=>
	{
		cfg.CreateMap<Player, PlayerDto>()
			.ForMember(d=>d.TeamIds, o=>o.MapFrom(s=>s.Teams.Select(t=>t.Id).ToList()))
			.ForMember(d=>d.FullName, o=>o.MapFrom(s=>s.Name + " " +s.LastName));
	});
	Mapper.AssertConfigurationIsValid();
	using(var connection = new SQLiteConnection("data source=test"))
	{
		var context = new MyDbContext(connection);
		LINQPad.Util.ClearResults();
		var players = context.Players.ProjectTo<PlayerDto>().Where(p=>p.FullName.Contains("P")).Dump();
		//context.Players.Select(p=>new PlayerDto { TeamIds = p.Teams.Select(t=>t.Id).ToList() }).Dump();
	}
}

class MyDbContext : DbContext
{
    public MyDbContext(SQLiteConnection connection) : base(connection, false) 
	{
		Database.Log = s=>Console.WriteLine(s);
	}
  
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        var sqliteConnectionInitializer = new MyDbContextInitializer(modelBuilder);
        Database.SetInitializer(sqliteConnectionInitializer);
    }
	
	public DbSet<Player> Players { get; set; }
	public DbSet<Team> Teams { get; set; }
}

class MyDbContextInitializer : SqliteDropCreateDatabaseAlways<MyDbContext>
{
    public MyDbContextInitializer(DbModelBuilder modelBuilder) : base(modelBuilder)
	{
	}

    protected override void Seed(MyDbContext context)
    {
        context.Players.Add(new Player { Name = "P1", Teams = new List<Team> { new Team { Name = "T1" }}});
		context.Players.Add(new Player { Name = "P2", Teams = new List<Team> { new Team { Name = "T1" }}});
		context.Players.Add(new Player { Name = "P3", Teams = new List<Team> { new Team { Name = "T2" }}});
		context.Players.Add(new Player { Name = "P4", Teams = new List<Team> { new Team { Name = "T2" }}});
		context.Players.Add(new Player { Name = "P5", Teams = new List<Team> { new Team { Name = "T3" }}});
    }
}
	
public class Player
{
	public long Id { get; set; }
	public List<Team> Teams { get; set; }
	public string Name { get; set; }
	public string LastName { get; set; }
}

public class Team
{
	public long Id { get; set; }
	public string Name { get; set; }
}

public class PlayerDto
{
	public long Id { get; set; }
	public string FullName { get; set; }
	public List<long> TeamIds { get; set; }
}