I need to create a new control which is composed of a TextBox and a Button. The most concise way I’ve found at the moment is with a CusomControl like this:

• inherit from TextBox and add the functionality of the command that must happen with the Button

   public class MyTextBoxWithButton : TextBox
   {
       ...
       DefaultStyleKeyProperty.OverrideMetadata(typeof(MyTextBoxWithButton), new    FrameworkPropertyMetadata(typeof(MyTextBoxWithButton)));
       ...
  
       public SomeBehaviourForTheButtonCommand(){...}
   }
  

in a ResourceDictionary, clone ALL the default TextBox template and replace the border with something like

    <DockPanel>
        <Border>
        <Button>
    </DockPanel>

the part I don’t like is having cloned the ENTIRE TextBox default template.
I don’t like the unnecessary duplication and also the additional work if in the future I want to add e.g. dark theme.

I can reduce the duplication a bit by extending the type style

    <Style BasedOn="{StaticResource {x:Type TextBox}}" TargetType="{x:Type local:MyTextBoxWithButton}">

With this I can avoid some initial property setters but the definition of the ControlTemplate remains entirely duplicated.

The other solution would be to implement a UserControl, but the cost of the boiler plate on the DependencyProperty seems equally high and ugly to me.

In general is there a way to create a control while minimizing code and xaml duplication?