public void DeleteRelationship(string id)
{
Check.Id(id);
CheckIsReadOnly();
Relationships.Remove(id);
relationshipsCollection.Relationships.RemoveAll(r => r.Id == id);
if (Relationships.Count > 0)
using (Stream s = GetPart(RelationshipUri).GetStream())
WriteRelationships(relationships, s);
else
DeletePart(RelationshipUri);
}