C# C Linq：添加另一个连接条件

我有一个问题：

// Query: gets recipients that have not been sent yet....
var query = (from rec in ent.Recipients 
join ch in ent.CampaignHistories on rec.RecipientID equals ch.RecipientID
into chl
from x in chl.DefaultIfEmpty().Where(xx => !xx.RecipientID.HasValue)

select new BRecipient()  
 {
   Email = rec.Email,
   Name = rec.Name,
   RecipientID = rec.RecipientID
 }).Take(remaining);

这将基本上在SQL中执行左连接，相当于：

Select * FROM            Recipients AS R LEFT OUTER JOIN
                         CampaignHistory AS H ON R.RecipientID = H.RecipientID 
WHERE        (H.RecipientID IS NULL)

我想要的是：

Select * FROM            Recipients AS R LEFT OUTER JOIN
                             CampaignHistory AS H ON R.RecipientID = H.RecipientID
AND H.CampaignID <> 21 
    WHERE        (H.RecipientID IS NULL)

如何创建LINQ？

我相信它会是：

join ch in ent.CampaignHistories.Where(x=>x.CampaignID != 21)
    on rec.RecipientID equals ch.RecipientID

但老实说，我不明白你想做什么。你为什么不干脆做：

from rec in ent.Recipients
where !ent.CampaignHistories
          .Any(x=>x.RecipientID == rec.RecipientID && x.CampaignID != 21)
select ...

---

和H.CampaignID 21请将DefaultIfEmpty放在where条件之后。我已更新了我的代码段。请尝试一下，如果有任何问题，请告诉我。

var query = (from rec in ent.Recipients
             join ch in ent.CampaignHistories.Where(xx => !xx.RecipientID.HasValue && xx.CampaignID != 21) on rec.RecipientID equals ch.RecipientID
             into chl
             from x in chl.DefaultIfEmpty()

             select new BRecipient()
             {
                 Email = rec.Email,
                 Name = rec.Name,
                 RecipientID = rec.RecipientID
             }).Take(remaining);