A DD4T.net Implementation - A Dynamic Publication Resolver

In the previous post Simple Publication Resolver, I presented a simplistic way of putting generic pages into Publication context by identifying the Publication URL by just applying a regular expression to the URL path.

In this post, I present a proper Publication Resolver algorithm, for DD4T.net, that dynamically maps Publication IDs to Publication URLs and vice versa.

The interface of a Publication Resolver defines 2 methods: GetPublicationUrl and GetPublicationId, which provide retrieval functionality for mapped Publication ID and URL.

public interface IPublicationResolver
{
    string GetPublicationUrl(int publicationId);
    int GetPublicationId(string publicationUrl);
}

The implementing class, PublicationResolver, defines an algorithm that dynamically discovers the mapped ID for a given Publication URL and the other way around. It makes use of the Tridion Content Delivery API PublicationMetaFactory to retrieve the PublicationMeta object containing information about the given Publication:

public class PublicationResolver : IPublicationResolver
{
    private readonly IDictionary<string, int> mapUrlToId =

        new Dictionary<string, int>();
    private readonly IDictionary<int, string> mapIdToUrl =

        new Dictionary<int, string>();

    public string GetPublicationUrl(int publicationId)
    {
        if (mapIdToUrl.ContainsKey(publicationId))
        {
            return mapIdToUrl[publicationId];
        }
        else
        {
            PublicationMetaFactory factory = new PublicationMetaFactory();
            PublicationMeta meta = factory.GetMeta(publicationId);
            string url = meta == null ? string.Empty : meta.PublicationUrl;

            mapIdToUrl[publicationId] = url;
            mapUrlToId[url] = publicationId;

            return url;
        }
    }

    public int GetPublicationId(string publicationUrl)
    {
        if (mapUrlToId.ContainsKey(publicationUrl))
        {
            return mapUrlToId[publicationUrl];
        }
        else
        {
            PublicationMetaFactory factory = new PublicationMetaFactory();
            PublicationMeta meta = factory.GetMetaByPublicationUrl(publicationUrl).FirstOrDefault();
            int id = meta == null ? 0 : meta.Id;

            mapIdToUrl[id] = publicationUrl;
            mapUrlToId[publicationUrl] = id;

            return id;
        }
    }
}

The interface and class above can easily be put in Ninject as singleton mapping:

Bind<IPublicationResolver>().To<PublicationResolver>().InSingletonScope();

When using the Publication Resolver, we can easily retrieve Publication ID for a given URL or the other way around. The code below defines property PublicationResolver that is injected into the current class:

[Inject]
public virtual IPublicationResolver PublicationResolver { get; set; }

...

string url = PublicationResolver.GetPublicationUrl(44);
int id = PublicationResolver.GetPublicationId("/zh/cn/");