类型'System.Linq.IQueryable'1 [System.Int32]'不支持比较运算符 [英] Comparison operators not supported for type 'System.Linq.IQueryable`1[System.Int32]'

问题描述

我遇到了LTS问题 我的代码如下:

I met a issue with LTS My code as below:

return from p in _db.Companies
where p.Deleted == false &&
(from q in _db.Contacts_Companies
where q.ContactId == contactId && q.Deleted == false
select q.CompanyId).Equals(p.Id)
select p;

我知道问题来自CompanyId.Equals(Id) 它们都是Int32，但是我有点困惑，无法比较Int32? 如果我使用包含，它将不符合我的要求.

I know the issue comes from the CompanyId.Equals(Id) they are both Int32, but I am a bit confused that Int32 cannot be compared? If I use Contains, it wont match my requirement.

我该如何克服这个问题?

How could I overcome this issue?

推荐答案

问题源于您的子查询:

from q in _db.Contacts_Companies
where q.ContactId == contactId && q.Deleted == false
select q.CompanyId

这不会返回int-它会返回(如错误消息中所示)IQueryable<int>.

This doesn't return an int - it returns (as shown in your error message) IQueryable<int>.

也许您对linq的延迟执行语义有所了解?

Perhaps you're caught up on the deferred execution semantics of linq?

无论如何，要解决此问题，您需要将IQueryable<int>转换为简单的int.由于您总是希望得到一个结果，因此建议添加.First():

Anyway, to solve this you need to convert from the IQueryable<int> to a simple int. Since you're always expecting exactly one result, I'd suggest adding .First():

return from p in _db.Companies
where p.Deleted == false &&
(from q in _db.Contacts_Companies
where q.ContactId == contactId && q.Deleted == false
select q.CompanyId).First().Equals(p.Id)
select p;

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