Get list of Publications based on Target Type in WEB 8.5 using 2016 Core Service

Question

I have an old method(mentioned below) for GUI extension which works fine in Tridion 2011 and 2013 where I am passing Publication Target and get all child Publications. But now when I deployed that code to WEB 8.5 it's not working. Also, I am getting an error

Exception message: Unable to cast object of type Tridion.ContentManager.CoreService.Client.TargetTypeData to type Tridion.ContentManager.CoreService.Client.PublicationTargetData

It seems like PublicationTargetData is eliminated and not supported for Web 8.5. Please help me out to get rid of this issue.

public Dictionary<string, string> GetValidChildPublicationList(string PublishingTargetUri)
{
    var client = _CoreServiceSession.GetClient();
    string publicationUri = GetCurrentPublicationIdFromObj();
    _childPublications = new Dictionary<string, string>();
    List<string> validPublications = new List<string>();

    ///Gets the list of Publications exisitng for current Publishing Target
    PublicationTargetData target = (PublicationTargetData)client.Read(PublishingTargetUri, new ReadOptions());

    foreach (LinkToPublicationData pub in target.Publications)
    {
        validPublications.Add(pub.IdRef);
    }

    ///Gets the child publications of the current item's publications
    UsingItemsFilterData usingPublicationsFilter = new UsingItemsFilterData
    {
        BaseColumns = ListBaseColumns.IdAndTitle, // to specify the detail in the XML
        ItemTypes = new[] { ItemType.Publication },  // to specify certain items
    };

    IEnumerable<XElement> usingPublicationXMLList = from comp in client.GetListXml(publicationUri, usingPublicationsFilter).Elements()
                                                    select comp;

    ///Add the current publication information to list of valid publications
    PublicationData currentPublication = (PublicationData)client.Read(publicationUri, new ReadOptions());
    if (validPublications.Contains(currentPublication.Id))
        _childPublications.Add(currentPublication.Id, currentPublication.Title);

    ///If the Publication is present in 
    foreach (XElement element in usingPublicationXMLList)
    {
        if (validPublications.Contains(element.Attribute("ID").Value))
            _childPublications.Add(element.Attribute("ID").Value, element.Attribute("Title").Value);
    }

    return _childPublications;
}

Answer 1

Publication Targets are deprecated since SDL Web 8; you don’t need them anymore if you are using Topology Manager based publishing.

However, they are still there for backwards compatibility purposes (even if you use Topology Manager based publishing).

So, your error is not caused by SDL Web 8.5 itself. Unfortunately, you didn’t provide much context for the error, but I guess it happens on the line where an item with a given URI (PublishingTargetUri) is read and then cast to PublicationTargetData.

I guess that the PublishingTargetUri is the TCM URI of a Target Type, resulting in this type cast exception.

So: the cause of this error probably lies in the caller of this method which provides a Target Type ID rather than a Publication Target ID (or in the method itself because it can’t deal with that; after all the term Publishing Target is used to denote a Publication Target or Target Type).

UPDATE

Based on the additional information you provided (in comments below), you confirmed that you are retrieving a Target Type ID and then provide it to this method which assumes it is a Publication Target ID.

I think what you were doing before is find Publications mapped to the same Publishing Target (before: Publication Target). With Topology Manager based publishing, those mappings are defined in Topology Manager rather than in Content Manager. For example, run Get-TtmMapping in PowerShell.

Although Publication Targets still exist for Topology Manager based publishing, they are not used for those mappings anymore. Note that the Topology Manager has a public API, though: Tridion.TopologyManager.Client.dll