Question

我正试图绕过这个交叉连接（我之前从未见过的东西），以便我可以转换为LINQ。我不确定它想做什么：

Select various a,b,c,d, and e columns
From Fee a
inner Join FeeCategory b on a.CategoryID = b.FeeCategoryID
inner join FeeCompanyType c on a.FeeID = c.FeeID
cross join FeeType e
left outer join FeeTypeLink d on a.FeeID = d.FeeID and e.FeeTypeID = d.FeeTypeID

到

var q = (
    from fees in Session.Query<Fee>()
    join feeCategories in Session.Query<FeeCategory>() on fees.FeeCategory.Id equals feeCategories.Id
    join feeCompanyType in Session.Query<FeeCompanyType>() on fees.Id equals feeCompanyType.Fee.Id
**erm.....**
)

大脑崩溃，任何帮助都赞赏......

Answer 1

在那里抛出另一个from，因为从LINQ的角度来看，你并没有真正“加入”这些表。

from fees in Session.Query<Fee>()
join feeCategories in Session.Query<FeeCategory>() on fees.FeeCategory.Id equals feeCategories.Id
join feeCompanyType in Session.Query<FeeCompanyType>() on fees.Id equals feeCompanyType.Fee.Id
from feeType in Session.Query<FeeType>()
select ...

Answer 2

对于交叉加入，只需添加另一个from：

from fees in Session.Query<Fee>()
//cross join:
from feetypes in Session.Query<Session.Query<Fee>()
join ...
join ...
// left join:
join feetypelink in Session.Query<FeeTypeLink>() on 
new {fees.FeeID,feetypes.FeeTypeID} equals new{feetypelink.FeeID,feetypelink.FeeTypeID} 
into gr
from res in gr.DefaultIfEmpty() .....

Answer 3

原始查询是无意义的，并没有真正进行交叉连接

实际上它等同于

Select various a,b,c,d, and e columns 
From Fee a 
inner Join FeeCategory b on a.CategoryID = b.FeeCategoryID 
inner join FeeCompanyType c on a.FeeID = c.FeeID 
left join FeeTypeLink d on a.FeeID = d.FeeID 
left join Feetype e ON e.FeeTypeID = d.FeeTypeID

现在您应该可以轻松地将其转换为Linq to SQL。我没有那么多使用，所以会留下其他人填写细节。你不需要任何花哨的东西。

Answer 4

您可以使用：

from a in ctx.As
join b in ctx.Bs on a.ID equals b.IdOfA //inner join for entities without relationships
join c in ctx.Cs on 1 equals 1 //inner join with constant condition

尝试将交叉连接transact-sql转换为LINQ

4 个答案: