For creating XAML based solution for limiting which build controls are included in

DebugBuildOnly.cs

using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace OnlyIn
{
    public class DebugBuild : ContentControl
    {
        protected override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            var content = this.Content as UIElement;
            if (content != null)
            {
#if DEBUG
                content.Visibility = Visibility.Visible;
#else
                content.Visibility = Visibility.Collapsed;
#endif
            }
        }
    }
}

Don't use this. Instead use https://gist.github.com/mrlacey/69465b3297726abbd0635e00bb95a5a9