VisualBrush vb = new VisualBrush
{
    Stretch = Stretch.Fill,
    Visual = this.FindResource("appbar_edit_minus") as Visual
};

RelativeSource relativeSource = new RelativeSource
{
     Mode = RelativeSourceMode.FindAncestor,
     AncestorType = typeof(Button)
};            

Rectangle rectangle = new Rectangle
{
     Width = 14,
     Height = 14,
};
rectangle.SetBinding(Rectangle.FillProperty, new Binding("Foreground")
{
     RelativeSource = relativeSource
});

rectangle.OpacityMask = vb;

     Style btn_style = (Style)this.FindResource("MetroFlatButton");
     Button btn = new Button
{
     Name = $"sub_jbxx{jbxxnum}",
     ToolTip = "删除本行",
     IsEnabled = true,
     VerticalAlignment = VerticalAlignment.Center,
     Background = Brushes.Transparent,
     Style = btn_style
};