/// <summary>
/// Función que permite agregar una relación al DataModelDocumentWpf.
/// </summary>
/// <param name="newRelation">Relación a ser agregada.</param>
public void AddRelation(RelationWpf newRelation)
{
if (newRelation == null)
{
throw new ArgumentNullException("newRelation", "newRelation can not be null");
}
newRelation.ContextMenuDeleteClick += new RoutedEventHandler(newRelation_ContextMenuDeleteClick);
MyDataModel.AddRelation(newRelation);
}