Question

我想写一个linq查询，它连接一些表并返回一个自定义对象但是我遇到了很多表的问题，因为我没有任何对象可以使用。你最后会看到我有问题的linq查询但是现在让我告诉你我对Code First，流畅的API和SQL的看法：

以下是我需要使用的所有表（稍后您将看到带有sql语句的所有外键）：

用户配置
BusinessProfile
出价
招标
UserBusinessProfile 用户和商家资料的多对多表格

多对多的表格以protected override void OnModelCreating(DbModelBuilder modelBuilder)这种方式定义

// Many to many UserProfiles => BusinessProfiles
            modelBuilder.Entity<UserProfile>()
                .HasKey(primaryKey => primaryKey.Id)
                .HasMany(business => business.BusinessProfiles)
                .WithMany(user => user.UserProfiles)
                .Map(m => m.MapLeftKey("UserProfileId")
                .MapRightKey("BusinessProfileId")
                .ToTable("UserBusinessProfile"));

就在这里，我需要在我的linq查询中包含.ToTable（“UserBusinessProfile”）......

最后，我的 SQL语句我需要用linq编写（SQL语句按预期工作。）：

select * from UserProfile inner join UserBusinessProfile on UserProfile.Id = UserBusinessProfile.UserProfileId inner join BusinessProfile on BusinessProfile.Id = UserBusinessProfile.BusinessProfileId inner join Bid on Bid.UserProfileId = UserProfile.Id and Bid.BusinessProfileId = BusinessProfile.Id inner join Tender on Bid.TenderId = Tender.Id

我有linq查询：

from UserProfile in context.UserProfile
join UserBusinessProfile in context.UserBusinessProfile on new { Id = UserProfile.Id } equals new { Id = UserBusinessProfile.UserProfileId }
join BusinessProfile in context.BusinessProfile on new { Id = UserBusinessProfile.BusinessProfileId } equals new { Id = BusinessProfile.Id }
join Bid in context.Bid
      on new { UserProfileId = UserProfile.Id, BusinessProfileId = BusinessProfile.Id }
  equals new { Bid.UserProfileId, Bid.BusinessProfileId }
join Tender in context.Tender on new { TenderId = Bid.TenderId } equals new { TenderId = Tender.Id }
where
  UserProfile.Id == 1 &&
  BusinessProfile.Id == 1
select new CustomObject{
  ...
}

正如您所看到的，我无法使用linq查询中的context.UserBusinessProfile，因为我没有任何对象可以像其他表一样使用。我真的不知道如何做到这一点，或者我如何编写我的linq查询来完成任务。

感谢您的时间和帮助，

卡琳

换句话说，当您知道UserBusinessProfile是多对多的表时，如何从此SQL查询中编写linq查询？：

select * from UserProfile 
inner join UserBusinessProfile on UserProfile.Id = UserBusinessProfile.UserProfileId
inner join BusinessProfile on BusinessProfile.Id = UserBusinessProfile.BusinessProfileId
inner join Bid on Bid.UserProfileId = UserProfile.Id and Bid.BusinessProfileId = BusinessProfile.Id
inner join Tender on Bid.TenderId = Tender.Id
where UserProfile.Id = 1 and BusinessProfile.Id = 1

Answer 1

在LINQ中编写应该要容易得多。

from ubp in context.UserBusinessProfile 
where ubp.UserProfile.Id = 1 && ubp.BusinessProfile.Id = 1
select ubp.UserProfile
//you can pretty much do anything with Bid and Tender, 
//you should be able to access Bid from
//ubp.BusinessProfile.Bids 
//(I think multiple bids are available for a BusinessProfile)

Answer 2

我找到了要走的路。可能是它可以优化，但它的工作。

    from user in context.UserProfiles
                    from business in context.BusinessProfiles
                    join bid in context.Bids on new { UserProfileId = user.Id, BusinessProfileId = business.Id } equals new { bid.UserProfileId, bid.BusinessProfileId }
                    join tender in context.Tenders on new { TenderId = bid.TenderId } equals new { TenderId = tender.Id }
                    where business.Id == businessProfileId && user.Id == userProfileId && tender.Id == tenderId
select new CustomObject
{
...
}

使用多对多场景和其他表编写linq查询

2 个答案: