SelectMany inside SelectMany

Question

I tried both of this but didn't work? how to do that?

.SelectMany(x => x.SectionEvents).SelectMany(t => t.Section)

.SelectMany(x => x.SectionEvents.SelectMany(t => t.Section))

Error :

The type arguments for method 'System.Linq.Enumerable.SelectMany<TSource,TResult>(System.Collections.Generic.IEnumerable<TSource>, System.Func<TSource,System.Collections.Generic.IEnumerable<TResult>>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

EEvent.List<EEvent>("CalendarPeriodUId", ECalendarPeriod.Current().UId).Value.ToList()
                .SelectMany(x => x.SectionEvents.SelectMany(t => t.Section)).ToFCollection().Bind(ddlSection, "SectionName");

Answer 1

I think you want is to select all Sections from Events through a join table.

public class Event
{
    public ICollection<SectionEvent> SectionEvents { get; set; }
}
public class SectionEvent
{
    public Event Event { get; set; }
    public Section Section { get; set; }
}
public class Section
{
    public ICollection<SectionEvent> SectionEvents { get; set; }
}

If that so, then what you need is SelectMany and Select.

var q = events.SelectMany(e => e.SectionEvents).Select(se => se.Section);