C# 如何使用castle活动记录区分选择和分组？

如何使用LINQ或HQL执行以下SQL查询

SELECT `year`, `month`, COUNT(code_id) 
  FROM (SELECT DISTINCT request_codes_id AS code_id, 
    YEAR(requested) AS `year`, MONTH(requested) AS `month` FROM requests) r
  GROUP BY `year`, `month`
  ORDER BY `year`, `month`;

我尝试了以下方法：

var items = from r in TestaccountRequest.Queryable
            group r by r.RequestCodeId into g
            select g.First();
var grouped = from r in items
                group r by r.Requested.ToString("yyyyMM") into y
                select new { Year = y.First().Requested.Year, Month = y.First().Requested.Month, Count = y.Count() };

var items = from r in TestaccountRequest.Queryable
            group r by r.RequestCodeId into g
            select g.ElementAt(0);
var grouped = from r in items.ToList()
              group r by new { Year = r.Requested.Year,
                               Month = r.Requested.Month } into g 
              select new { g.Key.Year, g.Key.Month, Count = g.Count() };

它将

System.String抛出到字符串（System.String）NotSupportedException

更新：

---

第一个LINQ查询中的

g.First（）

似乎是导致问题的原因，因为如果我只运行第一个查询，我会得到一个

应该不可访问的代码

-异常，但如果我删除

.First（）

它“工作”，但不会返回我需要的内容。

改为使用匿名类型分组：

var grouped = from r in items
              group r by new { Year = r.Requested.Year,
                               Month = r.Requested.Month } into g 
              select new { g.Key.Year, g.Key.Month, Count = g.Count() };

---

我用以下方法解决了这个问题：

var items = from r in TestaccountRequest.Queryable
            group r by r.RequestCodeId into g
            select g.First();
var grouped = from r in items
                group r by r.Requested.ToString("yyyyMM") into y
                select new { Year = y.First().Requested.Year, Month = y.First().Requested.Month, Count = y.Count() };

var items = from r in TestaccountRequest.Queryable
            group r by r.RequestCodeId into g
            select g.ElementAt(0);
var grouped = from r in items.ToList()
              group r by new { Year = r.Requested.Year,
                               Month = r.Requested.Month } into g 
              select new { g.Key.Year, g.Key.Month, Count = g.Count() };

但这并不是最好的解决方案，因为所有对象都是从数据库中获取的，但至少它目前正在工作，但如果可用，请提供更好的解决方案

编辑：
我现在使用HQL解决了这个问题：

HqlBasedQuery query = new HqlBasedQuery(typeof(ActivationCodeTestaccountRequestRecord),
            "SELECT DISTINCT r.ActivationCodeId, YEAR(r.Requested), MONTH(r.Requested) " +
            "FROM ActivationCodeTestaccountRequestRecord r");
var items = from object[] row in (ArrayList)ActiveRecordMediator.ExecuteQuery(query)
            group row by new { Year = row[1], Month =row[2] } into g2
            select new { Year = g2.Key.Year, Month = g2.Key.Month, Count = g2.Count() };

---

@chrfin：它说了哪种方法吗？不真实；堆栈跟踪中的最后一行是

NHibernate.Hql.Ast.ANTLR.PolymorphicQuerySourceDetector.GetClassName（IASTNode querySource）

，但请查看我的问题更新。