public class RootObject
    {
        public int Id { get; set; }
        public string Code { get; set; }
        ......

        public IList<GlideObject> Glides { get; set; }
    }

    public class GlideObject
    {
        public int RootId { get; set; }
        public int GlideId { get; set; }
        ......
    }

    var rootList = from p in roots
        select new
        {
            Id = p.Id ,
            Code = p.Code,
            RootId = p.Glides.RootId // ???
            GlideId = p.Glides.GlideId, // ???
        };
我想等到一个平整的对象。
问号处应该怎么写？或者Linq表达式怎么写？

自己回答：

from p in roots
from g in p.Glides
select new
{
    Id = p.Id ,
    Code = p.Code,
    RootId = g.RootId,
    GlideId = g.GlideId
};