Как сделать выравнивание в FrameworkElementFactory?

Так не работает выравнивание:

DataTemplate template = new DataTemplate();
FrameworkElementFactory gr = new FrameworkElementFactory(typeof(Grid));
gr.SetValue(Grid.HorizontalAlignmentProperty, HorizontalAlignment.Left);
FrameworkElementFactory wp = new FrameworkElementFactory(typeof(WrapPanel));
wp.SetValue(WrapPanel.HorizontalAlignmentProperty, HorizontalAlignment.Left);
FrameworkElementFactory tb = new FrameworkElementFactory(typeof(TextBlock));
tb.SetValue(TextBlock.HorizontalAlignmentProperty, HorizontalAlignment.Left);
tb.SetValue(TextBlock.TextProperty, i.Name);//добавим текст

wp.AppendChild(tb);
gr.AppendChild(wp);
template.VisualTree = gr;
button.ContentTemplate = template;