A Simple, Integrated WPF Help System

using System;
using System.Collections.Generic;
using System.Linq;
using System.Resources;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Automation;
using System.Windows.Media.Effects;
using System.Windows.Controls.Primitives;

namespace WpfTestApp
{
    public partial class Window1 : Window
    {

        private DependencyObject CurrentHelpDO { get; set; }
        private Popup CurrentHelpPopup { get; set; }
        private bool HelpActive { get; set; }
        private MouseEventHandler _helpHandler = null;
        private readonly OuterGlowBitmapEffect YellowGlow =
            new OuterGlowBitmapEffect() { GlowColor = Colors.Yellow, GlowSize = 10, Noise = 1 };

        public Window1()
        {
            InitializeComponent();
        }

        private void winMain_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.Key == Key.F1)
            {
                e.Handled = true;
                ToggleHelp();
            }
        }

        private void ToggleHelp()
        {
            // Turn the current help off
            CurrentHelpDO = null;
            if (CurrentHelpPopup != null)
            {
                CurrentHelpPopup.IsOpen = false;
            }

            // Toggle current state; add/remove mouse handler
            HelpActive = !HelpActive;

            if (_helpHandler == null)
            {
                _helpHandler = new MouseEventHandler(winMain_MouseMove);
            }

            if (HelpActive)
            {
                winMain.MouseMove += _helpHandler;
            }
            else
            {
                winMain.MouseMove -= _helpHandler;
            }

            // Start recursive toggle at visual root
            ToggleHelp(canvMain);
        }

        private void ToggleHelp(DependencyObject dependObj)
        {
            // Continue recursive toggle. Using the VisualTreeHelper works nicely.
            for (int x = 0; x < VisualTreeHelper.GetChildrenCount(dependObj); x++)
            {
                DependencyObject child = VisualTreeHelper.GetChild(dependObj, x);
                ToggleHelp(child);
            }

            // BitmapEffect is defined on UIElement so our DependencyObject 
            // must be a UIElement also
            if (dependObj is UIElement)
            {
                UIElement element = (UIElement)dependObj;
                if (HelpActive)
                {
                    string helpText = AutomationProperties.GetHelpText(element);
                    if (!helpText.IsNothing())
                    {
                        // Any effect can be used, I chose a simple yellow highlight
                        ((UIElement)element).BitmapEffect = YellowGlow;
                    }
                }
                else if (element.BitmapEffect == YellowGlow)
                {
                    element.BitmapEffect = null;
                }
            }
        }

        private void winMain_MouseMove(object sender, MouseEventArgs e)
        {
            // You can check the HelpActive property if desired, however 
            // the listener should not be hooked up so this should not be firing
            HitTestResult hitTestResult = VisualTreeHelper.HitTest(((Visual)sender), e.GetPosition(this));
            if (hitTestResult.VisualHit != null && CurrentHelpDO != hitTestResult.VisualHit)
            {
                // Walk up the tree in case a parent element has help defined
                DependencyObject checkHelpDO = hitTestResult.VisualHit;
                string helpText = AutomationProperties.GetHelpText(checkHelpDO);
                while (helpText.IsNothing() && checkHelpDO != null && checkHelpDO != canvMain && checkHelpDO != winMain)
                {
                    checkHelpDO = VisualTreeHelper.GetParent(checkHelpDO);
                    helpText = AutomationProperties.GetHelpText(checkHelpDO);
                }

                if (helpText.IsNothing() && CurrentHelpPopup != null)
                {
                    CurrentHelpPopup.IsOpen = false;
                    CurrentHelpDO = null;
                }
                else if (!helpText.IsNothing() && CurrentHelpDO != checkHelpDO)
                {
                    CurrentHelpDO = checkHelpDO;
                    // New visual "stack" hit, close old popup, if any
                    if (CurrentHelpPopup != null)
                    {
                        CurrentHelpPopup.IsOpen = false;
                    }

                    // Obviously you can make the popup look anyway you want it to look 
                    // with any number of options. I chose a simple tooltip look-and-feel.
                    CurrentHelpPopup = new Popup()
                    {
                        AllowsTransparency = true,
                        PopupAnimation = PopupAnimation.Scroll,
                        PlacementTarget = (UIElement)hitTestResult.VisualHit,
                        IsOpen = true,
                        Child = new Border()
                        {
                            CornerRadius = new CornerRadius(10),
                            BorderBrush = new SolidColorBrush(Colors.Goldenrod),
                            BorderThickness = new Thickness(2),
                            Background = new SolidColorBrush(Colors.LightYellow),
                            Child = new TextBlock()
                            {
                                Margin = new Thickness(10),
                                Text = helpText.Replace("\\r\\n", "\r\n"),
                                FontSize = 14,
                                FontWeight = FontWeights.Normal
                            }
                        }
                    };
                    CurrentHelpPopup.IsOpen = true;
                }
            }
        }
    }
}