使用不存在和连接的 SQL 查询到 LINQ 语法

Question

我的 SQL 查询如下所示在 SQL 中运行良好 我需要将其转换为 LINQ 语法

SQL-

SELECT [Key], Id
FROM LocalizationKeys AS lk
WHERE NOT EXISTS (SELECT 1
                  FROM Languages AS l
                  JOIN LocalizationValues AS lv ON l.Id = lv.LanguageId
                  WHERE l.Title = 'en-US' AND lv.LocalizationKeyId = lk.Id)

我尝试过的LINQ语法

var result = 

(from lk in localizationKey    
where !(from l in lang
        join lv in localizationValue on l.Id equals lv.LanguageId
        where l.Title == "en-US" && lv.LocalizationKeyId == lk.Id select 1).FirstOrDefault()   

 select lk).ToList();

得到错误：

运算符“！”不能应用于“int”类型的操作数

有什么线索我在哪里犯错了吗？

Answer 1

你可以这样试试：

(from lk in localizationKey    
where (from l in lang
        join lv in localizationValue on l.Id equals lv.LanguageId
        where (l.Title == "en-US" && lv.LocalizationKeyId == lk.Id)   
       select l).FirstOrDefault() == null
 select lk).ToList();

或

(from lk in localizationKey    
where !(from l in lang
        join lv in localizationValue on l.Id equals lv.LanguageId
        where !(l.Title == "en-US" && lv.LocalizationKeyId == lk.Id) 
        select l).FirstOrDefault().Any()
 select lk).ToList();

Answer 2

试试这个：

(from lk in localizationKey    
where (from l in lang
        join lv in localizationValue on l.Id equals lv.LanguageId
        where !(l.Title == "en-US" && lv.LocalizationKeyId == lk.Id) select 1).FirstOrDefault()   

 select lk).ToList();

Answer 3

我认为您的原始查询很好，您只需要在 where 子句中添加另一对括号：

(from lk in localizationKey     
  where !((from l in lang
        join lv in localizationValue on l.Id equals lv.LanguageId
        where l.Title == "en-US" && lv.LocalizationKeyId == lk.Id select 1).Any())
 select lk).ToList();