Question

I a missing something here but I am not sure what is that. So I need a pair of eyes. I want to get blog posts which has certain tags associated with it. My model structure looks like as below:

public partial class BlogPost : IEntity {

    public BlogPost() {

        this.BlogPostComments = new HashSet<BlogPostComment>();
        this.BlogPostUrls = new HashSet<BlogPostUrl>();
        this.TagsForBlogPosts = new HashSet<TagsForBlogPost>();
    }

    public System.Guid Key { get; set; }
    public System.Guid LanguageKey { get; set; }
    public Nullable<int> SecondaryKey { get; set; }
    public string Title { get; set; }

    //...

    public virtual ICollection<BlogPostComment> BlogPostComments { get; set; }
    public virtual Language Language { get; set; }
    public virtual ICollection<BlogPostUrl> BlogPostUrls { get; set; }
    public virtual ICollection<TagsForBlogPost> TagsForBlogPosts { get; set; }
}

public partial class Tag : IEntity {

    public Tag() {

        this.TagsForBlogPosts = new HashSet<TagsForBlogPost>();
        this.TagsForDynamicPages = new HashSet<TagsForDynamicPage>();
    }

    public System.Guid Key { get; set; }
    public System.Guid LanguageKey { get; set; }
    public string TagName { get; set; }

    //...    

    public virtual Language Language { get; set; }
    public virtual ICollection<TagsForBlogPost> TagsForBlogPosts { get; set; }
    public virtual ICollection<TagsForDynamicPage> TagsForDynamicPages { get; set; }
}

public partial class TagsForBlogPost : IEntity {

    public System.Guid Key { get; set; }
    public System.Guid BlogPostKey { get; set; }
    public System.Guid TagKey { get; set; }

    public virtual BlogPost BlogPost { get; set; }
    public virtual Tag Tag { get; set; }
}

As input I have string[] tags which I need for a blog posts to have. For now, I can have the following code working:

public void Get(string[] tags) {

    var posts = dbConxtext.BlogPosts.Where(x => 
        x.TagsForBlogPosts.Any(y => tags.Contains(y.Tag.TagName)));

    //

}

But it generates an IN Clause which is not what I want. Here is the T-SQL which the above code generates:

SELECT 
[Extent1].[Key] AS [Key], 
[Extent1].[LanguageKey] AS [LanguageKey], 
[Extent1].[SecondaryKey] AS [SecondaryKey], 
[Extent1].[Title] AS [Title], 
[Extent1].[BriefInfo] AS [BriefInfo], 
[Extent1].[Content] AS [Content], 
[Extent1].[ImagePath] AS [ImagePath], 
[Extent1].[IsApproved] AS [IsApproved], 
[Extent1].[CreationIp] AS [CreationIp], 
[Extent1].[CreatedOn] AS [CreatedOn], 
[Extent1].[LastUpdateIp] AS [LastUpdateIp], 
[Extent1].[LastUpdatedOn] AS [LastUpdatedOn]
FROM [dbo].[BlogPosts] AS [Extent1]
WHERE  EXISTS (SELECT 
    1 AS [C1]
    FROM  [dbo].[TagsForBlogPosts] AS [Extent2]
    INNER JOIN [dbo].[Tags] AS [Extent3] ON [Extent2].[TagKey] = [Extent3].[Key]
    WHERE ([Extent1].[Key] = [Extent2].[BlogPostKey]) AND ([Extent3].[TagName] IN (N'nuget',N'mvc'))
)

What I want is to exact match to those tags. Any idea how I can achieve that?

Edit:

What I need is as below:

The Post A has tag1, tag2 and tag3. The post B has tag1, tag3. If the string array includes tag1 and tag2, only the Post A should be selected because it has both tag1 and tag2.

Answer:

I managed to get it working thanks to @msarchet. Here is the LINQ query:

public void Get(string[] tags) {

    var posts = dbConxtext.BlogPosts
        .Where(x => tags.All(t => x.TagsForBlogPosts.Any(y => y.Tag.TagName == t)));

    //

}

And generated T-SQL:

SELECT 
[Extent1].[Key] AS [Key], 
[Extent1].[LanguageKey] AS [LanguageKey], 
[Extent1].[SecondaryKey] AS [SecondaryKey], 
[Extent1].[Title] AS [Title], 
[Extent1].[BriefInfo] AS [BriefInfo], 
[Extent1].[Content] AS [Content], 
[Extent1].[ImagePath] AS [ImagePath], 
[Extent1].[IsApproved] AS [IsApproved], 
[Extent1].[CreationIp] AS [CreationIp], 
[Extent1].[CreatedOn] AS [CreatedOn], 
[Extent1].[LastUpdateIp] AS [LastUpdateIp], 
[Extent1].[LastUpdatedOn] AS [LastUpdatedOn]
FROM [dbo].[BlogPosts] AS [Extent1]
WHERE  NOT EXISTS (SELECT 
    1 AS [C1]
    FROM  (SELECT 
        N'nuget' AS [C1]
        FROM  ( SELECT 1 AS X ) AS [SingleRowTable1]
    UNION ALL
        SELECT 
        N'razor' AS [C1]
        FROM  ( SELECT 1 AS X ) AS [SingleRowTable2]) AS [UnionAll1]
    WHERE ( NOT EXISTS (SELECT 
        1 AS [C1]
        FROM  [dbo].[TagsForBlogPosts] AS [Extent2]
        INNER JOIN [dbo].[Tags] AS [Extent3] ON [Extent2].[TagKey] = [Extent3].[Key]
        WHERE ([Extent1].[Key] = [Extent2].[BlogPostKey]) AND ([Extent3].[TagName] = [UnionAll1].[C1])
    )) OR (CASE WHEN ( EXISTS (SELECT 
        1 AS [C1]
        FROM  [dbo].[TagsForBlogPosts] AS [Extent4]
        INNER JOIN [dbo].[Tags] AS [Extent5] ON [Extent4].[TagKey] = [Extent5].[Key]
        WHERE ([Extent1].[Key] = [Extent4].[BlogPostKey]) AND ([Extent5].[TagName] = [UnionAll1].[C1])
    )) THEN cast(1 as bit) WHEN ( NOT EXISTS (SELECT 
        1 AS [C1]
        FROM  [dbo].[TagsForBlogPosts] AS [Extent6]
        INNER JOIN [dbo].[Tags] AS [Extent7] ON [Extent6].[TagKey] = [Extent7].[Key]
        WHERE ([Extent1].[Key] = [Extent6].[BlogPostKey]) AND ([Extent7].[TagName] = [UnionAll1].[C1])
    )) THEN cast(0 as bit) END IS NULL)
)

Answer 1

So what your trying to do per your comment

yes. Assuming: the Post A has tag1, tag2 and tag3. The post B has tag1, tag3. If the string array includes tag1 and tag2, the Post A should be selected.

Is

var posts = dbConxtext.BlogPosts.Where(x => tags.All(t => 
  x.TagsForBlogPost.Any(y => y.Tag.TagName == t)));

So make sure that All of the tags are contained in TagsForBlogPost

Warning, this may produce terrible SQL