Currently no free workshops planned, check out the full course list.

Composite WPF and Merged Dictionaries


No items found

Table of Contents

If, like me, you like to have changeable resource files in your application. Wither it is for changing the Theme, or interchanging templates you will need to take special care when using the


The new version of the TFS Sticky Buddy uses both!


I am using the built in Infragistics theme system, and the first time you select a theme I am just adding a resource file that overrides the default:

   1: Dim resourceDictionary As ResourceDictionary = ThemeManager.GetResourceSet(theme, ThemeManager.AllGroupingsLiteral)
   2: If Not resourceDictionary Is Nothing Then
   3:    Application.Current.Resources.MergedDictionaries.Add(resourceDictionary)
   4: End If


This causes an error in the ItemsControlRegionAdapter as WPF seams to redo the region adapters and you get a ItemsControlHasItemsSourceException. You need to change the code to the following (notice the commented out areas):

   1: /// <summary>
   2: /// Adapts an <see cref="ItemsControl"/> to an <see cref="IRegion"/>.
   3: /// </summary>
   4: /// <param name="region">The new region being used.</param>
   5: /// <param name="regionTarget">The object to adapt.</param>
   6: protected override void Adapt(IRegion region, ItemsControl regionTarget)
   7: {  //Modified by Martin Hinshelwood to allow resource file changes...
   8:     //if (regionTarget.ItemsSource != null || (BindingOperations.GetBinding(regionTarget, ItemsControl.ItemsSourceProperty) != null))
   9:     //    throw new InvalidOperationException(Resources.ItemsControlHasItemsSourceException);
  11:     //If control has child items, move them to the region and then bind control to region. Can't set ItemsSource if child items exist.
  12:     if (regionTarget.Items.Count > 0)
  13:     {
  14:         foreach (object childItem in regionTarget.Items)
  15:         {
  16:             region.Add(childItem);
  17:         }
  18:         //Control must be empty before setting ItemsSource
  19:         regionTarget.ItemsSource = null;
  20:         //regionTarget.Items.Clear();
  21:     }
  22:     regionTarget.ItemsSource = region.Views;
  23: }


You will notice that I had to comment out the exception for existing controls as well as the Items.Clear (which is replaced by setting the ItemsSource to nothing). This solves the problem I I have not noticed any adverse reactions.

The second problem occurs when you do you second set of the theme. at this point you need to remove the existing theme:

   1: If Not m_CurrentTheme Is Nothing Then
   2:       Application.Current.Resources.MergedDictionaries.Remove(m_CurrentTheme)
   3: End If


When this happens the region management is redone and you get a further RegionNameExistsException from the RegionManager. Then can be solved by changing the code in the AttachNewRegion method:

   1: /// <summary>
   2: /// Attaches a region to an object and adds it to the region manager.
   3: /// </summary>
   4: /// <param name="regionTarget">The object to adapt. This is typically a container (i.e a control).</param>
   5: /// <param name="regionName">The name of the region to register.</param>
   6: /// <exception cref="ArgumentException">When regions collection already has a region registered using <paramref name="regionName"/>.</exception>
   7: public void AttachNewRegion(object regionTarget, string regionName)
   8: {  //Modified by Martin Hinshelwood to allow resource file changes...
   9:     if (Regions.ContainsKey(regionName))
  10:         return; //throw new ArgumentException(string.Format(CultureInfo.InvariantCulture, Resources.RegionNameExistsException, regionName));
  12:     IRegionAdapter regionAdapter = regionAdapterMappings.GetMapping(regionTarget.GetType());
  13:     IRegion region = regionAdapter.Initialize(regionTarget);
  15:     Regions.Add(regionName, region);
  16: }


So instead of bombing out when you try to add a region of the same name, it will just ignore it. Not ideal, but necessary.


Technorati Tags:

Create a conversation around this article

Share on facebook
Share on Facebook
Share on twitter
Share on Twitter
Share on linkedin
Share on Linkdin

Want to learn more?

Check out the many training classes that we have.

No items found

Want to read more?


We believe that every company deserves high quality software delivered on a regular cadence that meets its customers needs. Our goal is to help you reduce your cycle time, improve your time to market, and minimise any organisational friction in achieving your goals.

naked Agility Limited is a professional company that offers training, coaching, mentoring, and facilitation to help people and teams evolve, integrate, and continuously improve.

We recognise the positive impact that a happy AND motivated workforce, that has purpose, has on client experience. We help change mindsets towards a people-first culture where everyone encourages others to learn and grow. The resulting divergent thinking leads to many different ideas and opportunities for the success of the organisation.