如何使用Linq和存储库模式导航导航属性？

Question

Using the Geneic Unit of Work and Repository Framework , I am trying to navigate navigation properties with Linq to Entities.

In my controller, I am using a repository pattern and unit of work. In this controller, the _repository is Websites .

Given the following three tables:

I am trying to get the Website entity, as well as a distinct list of ContentTypes.Description for all SourceUrls for a specific WebsiteID and UserId .

I can get the initial part of my data:

var website = _repository
    .Query()
    .Select()
    .Single(u => u.UserId == userId && u.WebsiteGuid == websiteGuid);

I have had several messy attempts, including something like this:

                    var website = _repository
                        .Query()
                        .Select()
                        .Single(u => u.UserId == userId && u.WebsiteGuid == websiteGuid)
                        .SourceUrls.Any(s => s.ContentTypeId == s.ContentType.ContentTypeId)
                        .Select(new ContentType());

The framework gives me the ability to write out a SQL query through .SelectQuery(...) , however I'm trying to avoid this.

I can create a new DTO and cast it to this as well.

Suggestions on how to get this Linq query to work?

Thanks.

--Update--

Trying this through the Website entity seems to be difficult as there is no direct navigation property Websites -- ContentTypes .

So, Starting from SourceUrls , I tried the following:

                    var rep2 = _unitOfWork.Repository<SourceUrl>()
                        .Query(q => q.UserId == userId)
                        .Include(i => i.ContentType.Description.Distinct())
                        .Include(i => i.Website)
                        .Select().Where(w => w.Website.WebsiteGuid == websiteGuid).ToList();

However I'm getting this new error:

"The Include path expression must refer to a navigation property defined on the type. Use dotted paths for reference navigation properties and the Select operator for collection navigation properties."

I also tried doing the linking through the .Select() but not quite there...

Answer 1

I don't have your data model to play with but this appears to be working on my local system:

using System.Linq;
using System.Data.Entity;

public class Class1
{
    public Class1()
    {
        var website = _repository
            .Where(w => w.UserId == userIdArg && w.WebsiteGuidArg == websiteGuidArg)
            .
    }
}

Your model may give you varying amounts of success with that Distinct() but the important things is that you can use include to make sure you get the collections loaded.

I've made this answer community wiki in case any new discoveries require a change to it.