LINQ query for tag system: Matching any of several tags?

I am just getting started with LINQ. I am creating an Entity Framework app that uses the canonical Post and Tag model. A Post contains an ID, Text, and Tags, a开发者_如何学编程nd a Tag contains an ID, a Name, and Posts.

A previous thread on StackOverflow showed me how to query for a Post that matches all Tag objects (A and B and C) in a search list. But how would I query for a Post that matches any Tag (A or B or C) in the list? Thanks for your help.

Stumbled over the answer right after I posted this question. PredicateBuilder to the rescue!

Here's my code, which uses PredicateBuilder. It is set up as an extension method:

public static IQueryable<Note> WhereContainsAnyTags(this IQueryable<Note> notes, IEnumerable<Tag> searchTags)
{
    // Initialize
    var predicate = PredicateBuilder.False<Note>();

    // Select Notes that contain any search Tags
    foreach (var searchTag in searchTags)
    {
        var tag = searchTag;
        predicate = predicate.Or(note => note.Tags.Any(t => t.Id == tag.Id));
    }

    // Set return value
    return notes.AsExpandable().Where(predicate);
}

And here is how I call the code:

searchResults = m_ViewModel.ObjectContext.Notes.WhereContainsAnyTags(m_ViewModel.SearchTags);

Not sure if this would work or not, but worth a try anyway I guess if you are already using WhereIn.

var posts = context.Tags.WhereIn(tag => tag.Name, acceptableValues)
                        .SelectMany(t => t.Posts);

The WhereIn should give you all the tags that are part of the name, and the SelectMany should give you all the posts containing those tags.

You could aslo do it like this with Entity SQL

var post = ctx.Posts.Where("it.Tags.Id IN (1,2,3)");