SQL到LINQ拿到賽的所有值

Question

我怎樣才能改變這種查詢LINQ的C＃代碼，所有的記錄：

SELECT k1.Ad_Id FROM KeywordAdCategories k1, KeywordAdCategories k2 
WHERE k1.Keyword_Id = (SELECT Id FROM keywords WHERE name = 'ALFA') 
AND k2.Keyword_Id = (SELECT Id FROM keywords WHERE name = '145') 
AND k1.Ad_Id = k2.Ad_Id 

的IDEIA是建立基於在可以是N關鍵字的數量動態查詢（在例子中它們是2：ALFA和145）

由於

編輯：

KeywordAdCategory型號：

public class KeywordAdCategory 
{ 
    [Key] 
    [Column("Keyword_Id", Order = 0)] 
    public int Keyword_Id { get; set; } 

    [Key] 
    [Column("Ad_Id", Order = 1)] 
    public int Ad_Id { get; set; } 

    [Key] 
    [Column("Category_Id", Order = 2)] 
    public int Category_Id { get; set; } 
} 

關鍵字型號：

public class Keyword 
{ 
    // Primary properties 
    public int Id { get; set; } 
    public string Name { get; set; } 
} 

如果我有5個關鍵詞，我會得到：

SELECT k1.Ad_Id FROM KeywordAdCategories k1, KeywordAdCategories k2, KeywordAdCategories k3, KeywordAdCategories k4, KeywordAdCategories k5 
WHERE k1.Keyword_Id = (SELECT Id FROM keywords WHERE name = 'KEYWORD1') 
AND k2.Keyword_Id = (SELECT Id FROM keywords WHERE name = 'KEYWORD2') 
AND k1.Ad_Id = k2.Ad_Id 
AND k3.Keyword_Id = (SELECT Id FROM keywords WHERE name = 'KEYWORD3') 
AND k2.Ad_Id = k3.Ad_Id 
AND k4.Keyword_Id = (SELECT Id FROM keywords WHERE name = 'KEYWORD4') 
AND k3.Ad_Id = k4.Ad_Id 
AND k5.Keyword_Id = (SELECT Id FROM keywords WHERE name = 'KEYWORD5') 
AND k4.Ad_Id = k5.Ad_Id 

Answer 1

public static int GetAdId(string KeywordId) 
{ 
    var dbContext = new MyDbContext(); 

    var result = (from k in in dbContext.KeywordAdCategories 
        where k.Keyword_Id == KeywordId 
        select k.Ad_Id).SingleOrDefault(); 

    return result; 
} 

運行的所有關鍵字，通過這種方法，IDS，你會得到相應的廣告ID 。我建議你閱讀LINQ。一旦你瞭解它，它是一個很棒的工具，雖然它起初看起來有點可怕，但這並不難學。 Pluralsight.com有很多是很容易掌握，並從:)

Answer 2

List<string> keywordnames = new List<string>(); 
// populate keywordsnames list  

IQueryable<int> AdIds = from k in KeywordAdCategories 
    where 
     (from kw in Keywords where keywordnames.Contains(kw.name) select kw.id) 
     .Contains(k.keyword_id) 
    select k.Ad_Id; 

或

List<string> keywordnames = new List<string>(); 
// populate keywordsnames list 

List<int> keywordnameids = (from kw in ctx.Keywords 
          where keywordnames.Contains(kw.name) 
          select kw.id).ToList(); 

List<int> AdIds = (from k in ctx.KeywordAdCategories 
        where keywordnameids.Contains(k.Keyword_Id) 
        select k.Ad_Id).ToList(); 

Answer 3

學習這是相當有一點麻煩，我想，當第一次看它的偉大的影片，所以我可能過度思考它。但這裏有一個解決方案，我相信會爲你工作：

var keywordList = new List<string>(); 
keywordList.Add("ALFA"); 
keywordList.Add("145"); 

var results = KeywordAdCategories.Select (kac => kac.Ad_Id).Distinct() 
      .Select (a => 
       new 
       { 
        AdId=a, 
        Keywords=KeywordAdCategories.Where(kac => kac.Ad_Id == a).Select(kac => kac.Keyword_Id) 
       }) 
      .Where(ac => ac.Keywords.Intersect(Keywords.Where(kw => keywordList.Contains(kw.Name)).Select (kw => kw.Id)).Count() == keywordList.Count()) 
      .Select (ac => ac.AdId); 

現在來解釋我在這裏做了什麼。首先，我想，所以我們這一行，開始與所有可能的廣告的ID：

KeywordAdCategories.Select (kac => kac.Ad_Id).Distinct() 

當然，這也許可以更容易地從一個不同的選擇取回從廣告表格，但我想唯一的工作與你所定義的。

接下來，我選擇的關鍵字及其相關集合中的每個廣告ID爲匿名列表類型的對象：

.Select (a => 
       new 
       { 
        AdId=a, 
        Keywords=KeywordAdCategories.Where(kac => kac.Ad_Id == a).Select(kac => kac.Keyword_Id) 
       }) 

接下來，我篩選結果只包含關鍵詞的集合，與相交的對象我們關鍵字列表，並具有與我們的關鍵字列表相同數量的結果元素。

.Where(ac => ac.Keywords.Intersect(Keywords.Where(kw => keywordList.Contains(kw.Name)).Select (kw => kw.Id)).Count() == keywordList.Count()) 

，最後我選擇了剛剛的廣告ID所導致

.Select (ac => ac.AdId); 

這裏是emmited SQL如果您位數的

-- Region Parameters 
DECLARE @p0 NVarChar(1000) = 'ALFA' 
DECLARE @p1 NVarChar(1000) = '145' 
DECLARE @p2 Int = 2 
-- EndRegion 
SELECT [t1].[Ad_Id] 
FROM (
    SELECT DISTINCT [t0].[Ad_Id] 
    FROM [KeywordAdCategories] AS [t0] 
    ) AS [t1] 
WHERE ((
    SELECT COUNT(*) 
    FROM (
     SELECT DISTINCT [t2].[Keyword_Id] 
     FROM [KeywordAdCategories] AS [t2] 
     WHERE (EXISTS(
      SELECT NULL AS [EMPTY] 
      FROM [Keywords] AS [t3] 
      WHERE ([t2].[Keyword_Id] = [t3].[Id]) AND ([t3].[Name] IN (@p0, @p1)) 
      )) AND ([t2].[Ad_Id] = [t1].[Ad_Id]) 
     ) AS [t4] 
    )) = @p2 

我相信有更優雅方法來完成你想要做的事情，但我想看看是否可以在一個linq查詢中完成所有事情。希望這可以幫助。