Question

您好我有以下结构：

Table Countries:
- CountryID
- CountryName

Table Records:
- RecordID
- RecordName
- CountryID

此LINQ返回所有国家/地区的列表＆＃34;以及＃34;：

 (from i in db.Countries 
 select new SelectListItem() 
 { 
     Text = i.CountryName, 
     Value = i.CountryID.ToString() 
 }).ToList();

我想以这样的方式对这个国家列表进行排序：＆＃34;记录＆＃34;中最受欢迎的国家/地区。表到顶部列表。怎么做？

Answer 1

  var  recordsItem=db.Records.GroupBy(x=> x.CountryID).Select( gr => new{ CID=gr.Key, Count=gr.Count()}).ToList();

  var result= (from c in db.Countries
              join  r in  recordsItem on c.CountryID equals r.CID
              order by r.Count descending
              select  new  SelectListItem() 
               {
                  Text = c.CountryName, 
                  Value =   c.CountryID.ToString()
               }).ToList();

Answer 2

您可以尝试这样的事情

(from i in db.Countries 
 join r in db.Records on i.CountryID equals r.CountryID into rds
 orderby rds.Count() descending
 select new SelectListItem() 
 { 
     Text = i.CountryName, 
     Value = i.CountryID.ToString() 
 }).ToList();

LINQ - 无法创建请求

2 个答案: