private void AddAttribute_Execute(object parameter)
        {
            PssgNodeViewModel  nodeView = (PssgNodeViewModel)parameter;
            AddAttributeWindow aaw      = new AddAttributeWindow();

            if (aaw.ShowDialog() == true)
            {
                PssgAttribute attr = nodeView.Node.AddAttribute(aaw.AttributeName, Convert.ChangeType(aaw.Value, aaw.AttributeValueType));
                if (attr == null)
                {
                    return;
                }

                nodeView.IsSelected = false;
                nodeView.IsSelected = true;
            }
        }
        private void AddAttributeCommandExecute(object obj)
        {
            var addAttributeWindow = new AddAttributeWindow(new AddAttributeViewModel());

            if (!addAttributeWindow.ShowDialog().GetValueOrDefault())
                return;

            var dataContext = addAttributeWindow.DataContext as AddAttributeViewModel;
            if (dataContext != null)
            {
                Attributes.Add(dataContext.Attribute);
            }

            InvalidateCommands();
        }