Alright, let's try this again
If you're trying to parse a comma seperated list you can use the following methods, this assume you already have an Article object called "a"
foreach (Tag t in Tag.ParseTags(post.mt_keywords, portalId))
{
ItemTag it = ItemTag.Create();
it.TagId = Convert.ToInt32(t.TagId, CultureInfo.InvariantCulture);
a.Tags.Add(it);
}
That will look up a tag in the database, if it doesn't exist it will add it to the database, and then return the proper information to be added to the article.tags collection.
Hopefully that helps, if not please let me know.