/// <summary>
/// Registers a document to use a shared paragragraph collection, which potentially may ensure uniqueness among many documents.
/// </summary>
/// <param name="shared">Shared collection feature.</param>
/// <param name="doc">Document to register with shared paragraph collection.</param>
/// <returns></returns>
public static ISharedFeature <IParagraphIdCollectionFeature> Add(this ISharedFeature <IParagraphIdCollectionFeature> shared, WordprocessingDocument doc)
{
doc.AddPackageEventsFeature();
doc.AddParagraphIdFeature();
var paragraphIdCollection = doc.Features.GetRequired <IParagraphIdCollectionFeature>();
shared.Add(paragraphIdCollection);
doc.Features.SetDisposable(new ParagraphIdSnapshotGenerator(paragraphIdCollection, shared, doc.Features.GetRequired <IPackageEventsFeature>()));
doc.Features.Set(shared);
doc.Features.Set(shared.Composite);
return(shared);
}