problem with inner join in many-to-many relationships with entity framework core 5

Question

I want to launch a query crossing two tables that are related from many to many and in entity framework core 5, it is not necessary to create the c# class of the intermediate table. So with include I launch the query with left join which is correct, but I need to launch an inner join and I can't because I don't have the c# class of the intermediate table. How would it be possible to do this without having to create the c# class of the intermediate table?

thank you very much

Answer 1

You don't need intermediate entity in order to achieve inner join in a LINQ to Entities query. All you need is SelectMany without DefaultIfEmpty().

For instance, using the sample model from Many-to-many section of the documentation:

public class Post
{
    public int PostId { get; set; }
    public string Title { get; set; }
    public string Content { get; set; }

    public ICollection<Tag> Tags { get; set; }
}

public class Tag
{
    public string TagId { get; set; }

    public ICollection<Post> Posts { get; set; }
}

the following will generate inner join:

var query = from post in db.Posts
            from tag in post.Tags
            select new { post, tag };

or with method syntax

var query = db.Posts
    .SelectMany(post => post.Tags, (post, tag) => new { post, tag });