在 LINQ to Entities 查询中无法构造实体或复杂类型

[code=language-cs]var orders = db.Orders.Where(o => o.UserId == userid).Select(c =>
new Order
{

OrderId = c.OrderId,
OrderDate = c.OrderDate,
Total = c.Total,
OrderDetails = db.OrderDetails.Where(od => od.OrderId == c.OrderId).ToList()

}
).ToList();

[code=language-cs]var orders = db.Orders.Where(o => o.UserId == userid).ToList().Select
(c =>
new Order
{OrderId = c.OrderId,
OrderDate = c.OrderDate,
Total = c.Total,
OrderDetails = db.OrderDetails.Where(od => od.OrderId == c.OrderId).ToList()}).ToList();

[code=plain]  public List<CMS_MudidiTag_Area> GetAreaTagDataByMonth(int tagMonth, int tagType, int tagId = 0)
{
List<CMS_MudidiTag_Area> listTag = new List<CMS_MudidiTag_Area>();
using (var context = new CMSContext())
{
listTag = context.CMS_MudidiTag_Area
.Where(t => t.TagMonth == tagMonth && t.Status == 0 && t.TagType == tagType && (tagId == 0 || t.TagId == tagId))
.Join(context.CMS_MudidiTag_Info, a => a.TagId, i => i.TagId, (a, i) => new { Id = a.Id, TagName = a.TagName, TagAlias = i.InfoName }).ToList()
.Select(r => new CMS_MudidiTag_Area { Id = r.Id, TagName = r.TagName, TagAlias = r.TagAlias }).ToList();
}
return listTag;
}