Easy help with WPF

If, like me, you like your applications to provide Context sensitive help, you’ve probably had a play around with the ApplicationCommands.Help command. In order to simplify hooking your help into your application, I’ve written the following code.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Input;
using form = System.Windows.Forms;
using System.Windows.Media;

namespace HelpProvider
{
  /// <summary>
  /// This class provides the ability to easily attach Help functionality 
  /// to Framework elements. To use it, you need to
  /// add a reference to the HelpProvider in your XAML. The FilenameProperty
  /// is used to specify the name of the helpfile, and the KeywordProperty specifies
  /// the keyword to be used with the search.
  /// </summary>
  /// <remarks>
  /// The FilenameProperty can be at a higher level of the visual tree than
  /// the KeywordProperty, so you don't need to set the filename each time.
  /// </remarks>
  public static class Help
  {
    /// <summary>
    /// Initialize a new instance of <see cref="Help"/>.
    /// </summary>
    static Help()
    {
      // Rather than having to manually associate the Help command, let's take care
      // of this here.
      CommandManager.RegisterClassCommandBinding(typeof(FrameworkElement),
        new CommandBinding(ApplicationCommands.Help,
          new ExecutedRoutedEventHandler(Executed),
          new CanExecuteRoutedEventHandler(CanExecute)));
    }

    #region Filename

    /// <summary>
    /// Filename Attached Dependency Property
    /// </summary>
    public static readonly DependencyProperty FilenameProperty =
      DependencyProperty.RegisterAttached("Filename", typeof(string), typeof(Help));

    /// <summary>
    /// Gets the Filename property.
    /// </summary>
    public static string GetFilename(DependencyObject d)
    {
      return (string)d.GetValue(FilenameProperty);
    }

    /// <summary>
    /// Sets the Filename property.
    /// </summary>
    public static void SetFilename(DependencyObject d, string value)
    {
      d.SetValue(FilenameProperty, value);
    }

    #endregion
    
    #region Keyword

    /// <summary>
    /// Keyword Attached Dependency Property
    /// </summary>
    public static readonly DependencyProperty KeywordProperty =
      DependencyProperty.RegisterAttached("Keyword", typeof(string), typeof(Help));

    /// <summary>
    /// Gets the Keyword property.
    /// </summary>
    public static string GetKeyword(DependencyObject d)
    {
      return (string)d.GetValue(KeywordProperty);
    }

    /// <summary>
    /// Sets the Keyword property.
    /// </summary>
    public static void SetKeyword(DependencyObject d, string value)
    {
      d.SetValue(KeywordProperty, value);
    }
    #endregion

    #region Helpers
    private static void CanExecute(object sender, CanExecuteRoutedEventArgs args)
    {
      FrameworkElement el = sender as FrameworkElement;
      if (el != null)
      {
        string fileName = FindFilename(el);
        if (!string.IsNullOrEmpty(fileName))
          args.CanExecute = true;
      }
    }

    private static void Executed(object sender, ExecutedRoutedEventArgs args)
    {
      // Call ShowHelp.
      DependencyObject parent = args.OriginalSource as DependencyObject;
      string keyword = GetKeyword(parent);
      if (!string.IsNullOrEmpty(keyword))
      {
        form.Help.ShowHelp(null, FindFilename(parent), keyword);
      }
      else
      {
        form.Help.ShowHelp(null, FindFilename(parent));
      }
    }

    private static string FindFilename(DependencyObject sender)
    {
      if (sender != null)
      {
        string fileName = GetFilename(sender);
        if (!string.IsNullOrEmpty(fileName))
          return fileName;
        return FindFilename(VisualTreeHelper.GetParent(sender));
      }
      return null;
    }
    #endregion

  }
}

Using it couldn’t be simpler, set up the Filename in your XAML and add any keywords you need to search on against your FrameworkElement items. The advantage of this approach is that you can bind different parts of your UI to different helpfiles if you want.

<Window 
  x:Class="HelpSample.Window1"
  xmlns="<a href="http://schemas.microsoft.com/winfx/2006/xaml/presentation">http://schemas.microsoft.com/winfx/2006/xaml/presentation</a>"
  xmlns:x="<a href="http://schemas.microsoft.com/winfx/2006/xaml">http://schemas.microsoft.com/winfx/2006/xaml</a>"
  Title="Window1" Height="300" Width="300"
  xmlns:help="clr-namespace:HelpProvider;assembly=HelpProvider"
  help:Help.Filename="MyHelpfile.chm"
  >
  <Grid>
    <Grid.RowDefinitions>
      <RowDefinition />
      <RowDefinition />
    </Grid.RowDefinitions>
    <TextBox help:Help.Keyword="MyKeyword" Grid.Row="0" Text="Keyword based search" />
    <TextBox Grid.Row="1" Text="No keyword" />
  </Grid>
</Window>

I hope this helps you as much, as it helps me.