Merged ResourceDictionaries

 
<Application.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="Styles/DefaultStyle.xaml"/>
        </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
</Application.Resources>
 
 

 
<ResourceDictionary 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
 
    <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="DefaultStyle/Button.xaml"/>
    </ResourceDictionary.MergedDictionaries>
 
    <Style TargetType="Control" BasedOn="{StaticResource {x:Type Control}}" />
 
</ResourceDictionary>
 
 

 
<ResourceDictionary.MergedDictionaries>
   <SharedResourceDictionary Source="/MyControlLibrary;component/Themes/Brushes.xaml"  />
</ResourceDictionary.MergedDictionaries>
 
 

 
 
[assembly: XmlnsDefinition("http://schemas.microsoft.com/winfx/2006/xaml/presentation", 
"WPFTutorial.Utils")]
 
/// <summary>
/// The shared resource dictionary is a specialized resource dictionary
/// that loads it content only once. If a second instance with the same source
/// is created, it only merges the resources from the cache.
/// </summary>
public class SharedResourceDictionary : ResourceDictionary
{
    /// <summary>
    /// Internal cache of loaded dictionaries 
    /// </summary>
    public static Dictionary<Uri, ResourceDictionary> _sharedDictionaries =
        new Dictionary<Uri, ResourceDictionary>();
 
    /// <summary>
    /// Local member of the source uri
    /// </summary>
    private Uri _sourceUri;
 
    /// <summary>
    /// Gets or sets the uniform resource identifier (URI) to load resources from.
    /// </summary>
    public new Uri Source
    {
        get { return _sourceUri; }
        set
        {
            _sourceUri = value;
 
            if (!_sharedDictionaries.ContainsKey(value))
            {
                // If the dictionary is not yet loaded, load it by setting
                // the source of the base class
                base.Source = value;
 
                // add it to the cache
                _sharedDictionaries.Add(value, this);
            }
            else
            {
                // If the dictionary is already loaded, get it from the cache
                MergedDictionaries.Add(_sharedDictionaries[value]);
            }
        }
    }
}