class TransparentTexBox:TextBox {
static TransparentTexBox() {
Control.BackgroundProperty.OverrideMetadata(typeof(TransparentTexBox), new FrameworkPropertyMetadata(Brushes.Transparent));
Control.BorderThicknessProperty.OverrideMetadata(typeof(TransparentTexBox), new FrameworkPropertyMetadata(new Thickness(0d)));
}
}
用TextBlock
或者，继承TextBox，再把它的BackgroundProperty属性重写了，使用这个新控件代替TextBox