Previewing Microsoft Office Documents and PDF in WPF using a Preview Handler Host


I had recently to implement a mechanism for showing documents into a WPF application. The very first solution was to start a new process using the path of the selected file. The only condition for this to work it’s that the file extension should have been previously registered to be opened with an specific application. A drawback is that the document is shown by an external application that we are not able to handle (at all or at least easily).

Then the client decided showing documents by embedding them into the application. So, I started researching about how to display Portable documents, Word documents, Excel documents into a WPF application. Finally after some research I got to a nice solution which will display many documents formats with the only condition of having the proper software installed into the PC where the application is gonna run.

The Problem
Showing a office document (XLS, DOC, XLSX, DOCX) or portable document (PDF) into a WPF APP.

This is not a bullet proof solution, but it is kind extensible for brave developers. The relays on the installed Preview Handlers. For example for visualizing Microsoft Office documents you will have to have installed Microsoft Office in the computer where the application is going to run. It’s the same case for PDF files, where you need to have a Preview Handler installed.
Moreover, the technology of Preview Handler has been built using native code, in order to embedded into a WPF application the app will be hosting WinForm content, this introduces a different set of restrictions about the interaction of the control once it has been instantiated.

The Solution
Preview Handlers is a technology added into Windows Vista, and it’s meant to readonly quick preview of files. It’s available on Windows Explorer
Enabling Previews in Windows Vista Folders
The Microsoft article [1] about Preview Handlers has an utility application which lists the available preview handlers in your system. Moreover after some research, I found the first implementation in [2] which was using Windows Forms and C# for development. Finally I found a more elaborated solution from Coding4Fun [3]. Since this point the solution for WPF was straightforward because it was only matter of loading a WinForm contro into WPF by using Interop components.

1) Grab the code from http://c4fdevkit.codeplex.com/ project. To use the Preview Handler Host you will need only two projects.
/Preview Handlers/Source/VCS/PreviewHandlerFramework
/Preview Handlers/Source/VCS/PreviewHandlerHost

Compile them and the create a new WPF project. The codeplex project hasn’t been updated in awhile, thus you’re more likely to have to update the solution file to a new version of visual studio.

2) Add to your WPF application (or library) a reference to WindowsFormIntegration library. This will allow the application to host WinForm controls. Also add System.Windows.Forms since it will be required by the Preview Handler libraries.

3) The use the WindowsFormsHost tag to embed the PreviewHandlerHostControl as the follwing XAML shows:


            <C4F_DevKit_PreviewHandler_PreviewHandlerHost:PreviewHandlerHostControl x:Name="previewHandlerHostControlInstance" />

4) Finally our C# code that for our sample is quite simple. We just select a file and let the PreviewHandlerHost control do the work.

using System;
using System.Windows;

namespace PreviewHandlerWpfApplication
    public partial class MainWindow : Window
        public MainWindow()

        private void Button_Click(object sender, RoutedEventArgs e)
            var dlg = new Microsoft.Win32.OpenFileDialog();
            if (dlg.ShowDialog().Value)
                previewHandlerHostControlInstance.FilePath = dlg.FileName;

Here is an screenshot of my mighty document viewer:


Finally the code is available at GitHub https://github.com/hmadrigal/playground-dotnet/tree/master/MsDesktop.PreviewHandlers Have fun!




Customizable On Screen Keyboard (OSK) for WPF (it works for WebBrowser control)


Recently my colleagues and I faced a very particular problem in WPF. We were creating a very stylish application for a kiosk, and the keyboard should look different from the default OSK in WPF. At the beginning we import our old OSK which concatenates characters to a string, but this approach won’t work on the WebBrowser control since this control does not exposes internal components such as textbox. The following post is about my experience creating a solution for this particular problem.

The Problem

  • Customizable style for the on screen keyboard
  • The OSK must be able to interact with the WebControl control.

The solution

The default OSK

At first the most logical solution is to use the default. The problem with the default OSK is that it’s not possible to customize. Moreover the default OSK is not embedded into the WPF, it works on top of any other windows application.

Default Windows On Screen keyboard

Default Windows On Screen keyboard (OSK)

Appending strings

The our team decided to import our old OSK from a previous project. This first version of the OSK was a custom control. This custom control has a lot buttons and one string. Each time a button is pressed, a new character  is append to the string, thus the user of the control only have to check the current string in order to know which characters has been typed. The problem with this other approach is that keys like “arrows”, “control” or “alt” don’t have a way to represented into a string. At this time we’ve created out QueryKeyboard Contol which defines a bunch of buttons and appends characters to a string.

Customizing  a WPF OSK

Later on, we realize that our application will have to interact with the WebBrowser. Thus I decide we can use the same approach that the Wosk: Flexible On Screen Keyboard using WPF (http://wosk.codeplex.com/SourceControl/list/changesets) was using. Basically, WOSK was inserting keyboard  codes into the keyboard buffer, so the the operative system will report the input the the current focused window and control.

Thus, the approach was to separate the logic of the virtual keyboard from the keyboard control. So, the virtual keyboard could work as independent a service or be part of a more complex control such as the QueryKeyboardControl.

I’ve publish a sample of the project in Git Hub at https://github.com/hmadrigal/playground-dotnet/tree/master/MsDesktop.OnScreenKeyboard. The following items are the most relevant into the project sample:

  • Hmadrigal.Services.VirtualKeyboard: This projects holds the Service for a Virtual Keyboard.
    • NativeUser32.cs: Wrapper for Win32 low level calls
    • KeysEx.cs:  Known key codes. Set of known values to be inserted into the keyboard buffer.
    • VirtualKeyboardService.cs: Singleton class which exposes functionality in order to keep the state of the virtual keyboard.
  • Hmadrigal.WpfToolkit: This projects holds the visual representation for a on screen keyboard control in WPF.
    • QuertyKeyboard.cs: Custom control which keeps logic for appending strings or utilizing the virtual keyboard service.
    • Generic.xaml: Contains the default style for the custom control
    • WeakEventHandling.cs: Weak event handling (see references)
  • Hmadrigal.SampleKeyboard: WPF application using the custom keyboard with a web browser.

Querty Keyboard Control

Querty Keyboard Control using the virtual keyboard service


  • The default style has set the attribute “Focusable” to “False” in all the buttons (or any other item which can get  the focus). This should be done for any custom style. Because of the virtual keyboard service does not known who is going to handle the reported input, then the app is responsible of setting the focus to the proper item.
  • When debugging and using  keys like shift, alt, ctrl, those are kept pressed by the virtual keyboard service, but they will affect your debug execution because of the input is happening at the operative system level. So, be cautious about where the breakpoints are set.
  • Multilingual by using IME. Particularly I’ve set up my PC to use IMEI Japanese using romanji, so  FYI it will continue working ;-).
  • Because of the WebBrowser control is a Win32 interop control running on WPF, the default focus might no be on the WebBrowser contol. Sadly I don’t have a solution for this yet, just make sure that the user have an option to set the focus into the WebBrowser control once it has been loaded.


The sample code for this application is on Git Hub at:

NOTE (01/29/2014) Even at this time, this post continues to be one of the most viewed in my (humble) blog. However, I had forgotten to update this post in particular, at https://polaris.codeplex.com is the latest version of this keyboard (which is more likely to have less bugs and more flexibility such as a Debug Mode, and adding custom keys with more ease). My advice is to get the code and export the control, since the polaris libraries are meant for being downloaded and work all together, and you will be more likely to use only the keyboard.


How to make the Windows OSK open when a TextBox gets focus, instead of requiring users to tap a keyboard icon?

.NET Framework Developer Center / Creating custom InputDevice

Wosk: Flexible On Screen Keyboard using WPF

SendInput Example In C#

Simulating Keyboard with SendInput API in DirectInput applications

Generic implementation for a weak event handling

From Joel Pobar’s CLR weblog Creating delegate types via Reflection.Emit

Xhader 1.0 has been released!


This is my first open source project that I’ve been published. It’s not based on my code, it’s based on a set of several tools and helpers I’ve been able to find in the web. So, the project itself is just a easy way to access all that resources in one single point by using your Microsoft Blend tool.

Xhader 1.0 Summary

Xaml is a markup language based on xml, which is used to create presentation layer in your Microsoft Application e.g. Silverlight Applications and WPF applications. There is a particular feature that is available for certain users which is to use the support to modify the rendere

See more information at:


Best regards,