I am not quite sure I understand your issue. For starters, I don't know anything about "policystring". That does not appear anywhere in my code.
As you probably have seen in WpfMetadataExtractor, a metadata item is added to the collection like this:
Code:metadataItems.AddNew(int.MinValue, FormattedMetadataItemName.Title, Resources.Metadata_Title, bmpMetadata.Title, true);
That method has this signature:
Code:IGalleryObjectMetadataItem AddNew(int mediaObjectMetadataId, GalleryServerPro.Business.Metadata.FormattedMetadataItemName metadataItemName, string description, string value, bool hasChanges);
Basically, you are just adding two strings - the description and value. These are what appear in the two columns of the image metadata popup window. I assume you are able to get this info using your GetQuery technique.
So the only mystery is what do you use for the FormattedMetadataItemName? For that, I suggest adding items to this enum to match what you are adding. For example, if you want to add a metadata item named GPS coordinates, add an enum value GpsCoordinate to the enumeration.
If this didn't answer your question, let me know.
Roger Martin
Lead Developer for Gallery Server Pro