Question

我正在使用LINQPad将SQL转换为LINQ并在此过程中学习LINQ。我遇到了一些问题，并且希望有人可以查看我生成的LINQ代码，看看我是否在正确的轨道上？

这是我的SQL代码：

Select  Count(Convert(varchar(250), 
        Comment.CommentId)) as Num, 
        DiscussionBoard.ItemName, 
        Status.Status, 
        Status.Sequence

From    Comment inner join status on Comment.StatusID = Status.StatusID 
        inner join DiscussionBoard on Comment.DiscussionBoardID 
        = DiscussionBoard.DiscussionBoardID

WHERE   discussionboard.DiscussionBoardID 
        = '3ab7c139-317c-4450-9823-45a40ea6d0ff'

Group By status.Status, 
         Status.Sequence, 
         DiscussionBoard.ItemName
ORDER BY Status ASC

这是我到目前为止提出的LINQ代码。忍受我，我刚刚学习LINQ，我还没有完全理解它。任何指针都将非常感激：

from  Comment in Comments
where DiscussionBoard.DiscussionBoardID == '3ab7c139-317c-4450-9823-45a40ea6d0ff'

join  Status in Statuses on Comment.StatusID equals Statuses.StatusID
join  DiscussionBoard in DiscussionBoards on Comment.DiscussionBoardID equals DiscucussionBoard.DiscussionBoardID

group CountGroup by new {
                         Status.Status,
                         Status.Sequence,
                         DiscussionBoard.DiscussionBoardID
                        }

select new
{
    Count = CountGroup.Count(),
    DiscussionBoard.ItemName,
    Status.Status,
    Status.Sequence
}

Answer 1

group x by y

此片段结束查询。

我认为你的意思是：

group x by y into z

此片段在范围内继续使用z进行查询。并从范围中删除所有先前的范围变量。 z是IGrouping<y, x>，也就是说，密钥类型是y的类型，组元素类型是x＆＃39; s。

以下是我的查询：

from comment in Comments
where comment.DiscussionBoard.DiscussionBoardID == '3ab7c139-317c-4450-9823-45a40ea6d0ff'
let status = comment.Status
let board = comment.DiscussionBoard
group comment by new {
  status.Status,
  status.Sequence,
  board.ItemName
} into g
select new
{
    Count = g.Count(),
    ItemName = g.Key.ItemName,
    Status = g.Key.Status,
    Sequence = g.Key.Sequence
}

打开此查询的另一种方法是：

from board in DiscussionBoards
where board.DiscussionBoardID == '3ab7c139-317c-4450-9823-45a40ea6d0ff'
from comment in board.Comments

我在SQL到LINQ转换中做错了什么？

1 个答案: