Is there any good reason for a difference between PublishEngine.IsPublished() and the component xml field IsPublished?

Question

I'm trying to check if a binary is already published to the target and if not publish it.

private bool isCompToPublish(Component component)
{
    bool compToPublish = false;
    PublicationTarget target = new PublicationTarget(PublicationTargetId, component.Session);
    ICollection<PublishInfo> pubInfoCol = PublishEngine.GetPublishInfo(component);

    if (PublishEngine.IsPublished(component, target))
    {
        if (pubInfoCol.Where(a => a.PublicationTarget.Id == PublicationTargetId).Count() > 0)
        {
            PublishInfo pubInfo = pubInfoCol.Where(a => a.PublicationTarget.Id == PublicationTargetId).OrderBy(a => a.PublishedAt).Last();
            compToPublish = pubInfo.PublishedAt < component.RevisionDate;
        }
    }
    else
    {
        compToPublish = true;
    }
    return compToPublish;
}

But in some occasions it suddenly did republish the component. The check if (PublishEngine.IsPublished(component, target)) returned a false, although the binary is published to the target.

I even changed the check to if (PublishEngine.IsPublished(component)), but still it returns a false.

And when I check the components XML with: component.ToXml(XmlSections.Info).SelectSingleNode("/*/*/*/*[local-name()='IsPublished']").InnerText it returns a true.

The really weird stuff, is that some of the binaries do behave correctly.

All binaries use the same schema.

Update I went and checked the database and there is actually something different in the Item_States table. The binary that goes wrong:

And here the binary that works correctly:

Answer 1

Unless the binary has a Component Template associated with it, which is set to publish dynamically, your binary (even if placed directly on a Page) will never get a publish status of itself (same as with normal Components).

Only Pages and Dynamic Component Presentations (the Component and its dynamic Component Template) have a publish status which you can check through the API.

The difference between PublishEngine.IsPublished(component, target) and the Component XML IsPublished element, is that through the PublishEngine you can gather this information specifically for a given Publication Target, while the element in the Component XML just indicates if it ever has been published (so for any Publication Target). But as indicated above, this will only contain a value if the Component is part of a Dynamic Component Presentation.

So looking at your last comments, you say that it is working for some binaries while all the the same Schema. From that the only conclusion I can make is that at some point there has been a dynamic Component Template associated with the Schema of your Multimedia Components, and since that, any binary published would have gotten its publish status set.

Answer 2

The component XML "published" field only indicates if a component has been published as a DCP. Of it is published, in the CME you'll see a little globe icon next to the component icon within the publication from where it is published.

IsPublished(component, target) is the function to use, just make sure that the component is in the proper context publication. What I mean is, if it's a local item in your Global Content publication it will not be published, but if it's in the context of the web publication you actually publish from it will be published.