AdornerProvider Class

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Input;
using System.Windows;
using System.Windows.Automation;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Shapes;
using Microsoft.Windows.Design.Interaction;
using Microsoft.Windows.Design.Model;

namespace CustomControlLibrary.VisualStudio.Design
{
    // The following class implements an adorner provider for the 
    // adorned control. The adorner is a slider control, which 
    // changes the Background opacity of the adorned control.
    class OpacitySliderAdornerProvider : PrimarySelectionAdornerProvider
    {
        private ModelItem adornedControlModel;
        private ModelEditingScope batchedChange;
        private Slider opacitySlider;
        private AdornerPanel opacitySliderAdornerPanel;

        public OpacitySliderAdornerProvider()
        {
            opacitySlider = new Slider();
        }

        // The following method is called when the adorner is activated.
        // It creates the adorner control, sets up the adorner panel,
        // and attaches a ModelItem to the adorned control.
        protected override void Activate(ModelItem item)
        {
            // Save the ModelItem and hook into when it changes.
            // This enables updating the slider position when 
            // a new Background value is set.
            adornedControlModel = item;
            adornedControlModel.PropertyChanged += 
                new System.ComponentModel.PropertyChangedEventHandler(
                    AdornedControlModel_PropertyChanged);

            // Setup the slider's min and max values.
            opacitySlider.Minimum = 0;
            opacitySlider.Maximum = 1;

            // Setup the adorner panel.
            // All adorners are placed in an AdornerPanel
            // for sizing and layout support.
            AdornerPanel myPanel = this.Panel;

            // The slider extends the full width of the control it adorns.
            AdornerPanel.SetAdornerHorizontalAlignment( 
                opacitySlider, 
                AdornerHorizontalAlignment.Stretch);

            // Position the adorner above the control it adorns.
            AdornerPanel.SetAdornerVerticalAlignment(
                opacitySlider, 
                AdornerVerticalAlignment.OutsideTop);

            // Position the adorner 5 pixels above the control. 
            AdornerPanel.SetAdornerMargin(
                opacitySlider, 
                new Thickness(0, 0, 0, 5));

            // Initialize the slider when it is loaded.
            opacitySlider.Loaded += new RoutedEventHandler(slider_Loaded);

            // Handle the value changes of the slider control.
            opacitySlider.ValueChanged += 
                new RoutedPropertyChangedEventHandler<double>(
                    slider_ValueChanged);

            opacitySlider.PreviewMouseLeftButtonUp += 
                new System.Windows.Input.MouseButtonEventHandler(
                    slider_MouseLeftButtonUp);

            opacitySlider.PreviewMouseLeftButtonDown += 
                new System.Windows.Input.MouseButtonEventHandler(
                    slider_MouseLeftButtonDown);

            base.Activate(item);
        }

        // The Panel utility property demand-creates the 
        // adorner panel and adds it to the provider's 
        // Adorners collection.
        public AdornerPanel Panel 
        { 
            get
            {
                if (this.opacitySliderAdornerPanel == null)
                {
                    opacitySliderAdornerPanel = new AdornerPanel();

                    opacitySliderAdornerPanel.Children.Add(opacitySlider);

                    // Add the panel to the Adorners collection.
                    Adorners.Add(opacitySliderAdornerPanel);
                }

                return this.opacitySliderAdornerPanel;
            } 
        }


        // The following method deactivates the adorner.
        protected override void Deactivate()
        {
            adornedControlModel.PropertyChanged -= 
                new System.ComponentModel.PropertyChangedEventHandler(
                    AdornedControlModel_PropertyChanged);
            base.Deactivate();
        }

        // The following method handles the PropertyChanged event.
        // It updates the slider control's value if the adorned control's 
        // Background property changed,
        void AdornedControlModel_PropertyChanged(
            object sender, 
            System.ComponentModel.PropertyChangedEventArgs e)
        {
            if (e.PropertyName == "Background")
            {   
                opacitySlider.Value = GetCurrentOpacity();
            }
        }

        // The following method handles the Loaded event.
        // It assigns the slider control's initial value.
        void slider_Loaded(object sender, RoutedEventArgs e)
        {   
            opacitySlider.Value = GetCurrentOpacity();
        }

        // The following method handles the MouseLeftButtonDown event.
        // It calls the BeginEdit method on the ModelItem which represents 
        // the adorned control.
        void slider_MouseLeftButtonDown(
            object sender, 
            System.Windows.Input.MouseButtonEventArgs e)
        {
            batchedChange = adornedControlModel.BeginEdit();
        }

        // The following method handles the MouseLeftButtonUp event.
        // It commits any changes made to the ModelItem which represents the
        // the adorned control.
        void slider_MouseLeftButtonUp(
            object sender, 
            System.Windows.Input.MouseButtonEventArgs e)
        {
            if (batchedChange != null)
            {
                batchedChange.Complete();
                batchedChange.Dispose();
                batchedChange = null;
            }
        }

        // The following method handles the slider control's 
        // ValueChanged event. It sets the value of the 
        // Background opacity by using the ModelProperty type.
        void slider_ValueChanged(
            object sender, 
            RoutedPropertyChangedEventArgs<double> e)
        {
            double newOpacityValue = e.NewValue;

            // During setup, don't make a value local and set the opacity.
            if (newOpacityValue == GetCurrentOpacity())
            {
                return;
            }

            // Access the adorned control's Background property
            // by using the ModelProperty type.
            ModelProperty backgroundProperty = 
                adornedControlModel.Properties["Background"];
            if (!backgroundProperty.IsSet)
            {
                // If the value isn't local, make it local 
                // before setting a sub-property value.
                backgroundProperty.SetValue(backgroundProperty.ComputedValue);
            }

            // Set the Opacity property on the Background Brush.
            backgroundProperty.Value.Properties["Opacity"].SetValue(newOpacityValue);
        }

        // This utility method gets the adorned control's
        // Background brush by using the ModelItem.
        private double GetCurrentOpacity()
        {
            Brush backgroundBrushComputedValue =
                (Brush)adornedControlModel.Properties["Background"].ComputedValue;

            return backgroundBrushComputedValue.Opacity;
        }
    }
}