在 LINQ to SQL 中使用 Max

Question

在 LINQ to SQL 的 where 子句中使用 Max 时出现问题。数据如下：

QID,   Question,     TypeID,    Disable, VersionID, Sequence
1      Who's on 1st   1          False    1          1
2      Who's on 1st   1          False    2          1
3      What's on 2nd  1          False    1          2
4      What's on 2nd  1          False    2          2
5      I don't know   1          False    1          3
6      I don't know   1          False    2          3

我需要根据 VersionID 的最大值返回一组问题，如下所示。我期望从上面的数据得到的结果将包括第 2、4 和 4 行。 6 按顺序排序。

IEnumerable<QUESTION> questions = 
  (from q in dataContext.QUESTIONs
   where q.TypeID == Convert.ToInt16(ddlType.SelectedValue)
     && (q.Disable == null || q.bDisable == false)
     && (q.VersionID == dataContext.QUESTIONs.Max(q.nVersionID))
   orderby q.Sequence ascending
   select q);

Answer 1

Max() 在 linq-to-sql 中正确翻译

尝试

IEnumerable<QUESTION> questions = (from q in dataContext.QUESTIONs
                      let maxVersion = dataContext.QUESTIONs.Max(q.nVersionID)
                      where q.TypeID ==     Convert.ToInt16(ddlType.SelectedValue)
                      && (q.Disable == null || q.bDisable == false)
                      && (q.VersionID == maxVersion)
                      orderby q.Sequence ascending
                      select q);