Question

I’m am currently developing a silverlight application, I am still a beginner with this.
I am wondering if it is possible to change the resource dictionary’s source in code behind(C#)
within the App.xaml?
I have tried the code below, but get an exception, i am getting the style folder name from a WCF Service, the variable is called Style(this contains the name of the folder)

ResourceDictionary rDictionary = this.Resources.MergedDictionaries[0];
        rDictionary.Source = new Uri(string.Format("Resources/Styles/{0}/Styles.xaml", style), UriKind.Relative);
        this.Resources.MergedDictionaries.Add(rDictionary);

I’m getting an error at

rDictionary.Source = new Uri(string.Format("Resources/{0}/Styles.xaml", "Default"), UriKind.RelativeOrAbsolute);

Which reads

System.Exception: Error HRESULT E_FAIL has been returned from a call to a COM component.
   at MS.Internal.XcpImports.CheckHResult(UInt32 hr)
   at MS.Internal.XcpImports.SetValue(IManagedPeerBase obj, DependencyProperty property, String s)
   at MS.Internal.XcpImports.SetValue(IManagedPeerBase doh, DependencyProperty property, Object obj)
   at System.Windows.DependencyObject.SetObjectValueToCore(DependencyProperty dp, Object value)
   at System.Windows.DependencyObject.SetEffectiveValue(DependencyProperty property, EffectiveValueEntry& newEntry, Object newValue)
   at System.Windows.DependencyObject.UpdateEffectiveValue(DependencyProperty property, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, ValueOperation operation)
   at System.Windows.DependencyObject.SetValueInternal(DependencyProperty dp, Object value, Boolean allowReadOnlySet)
   at System.Windows.ResourceDictionary.set_Source(Uri value)
   at FCStarFish.App..ctor()

Answer 1

Does this work

<Application.Resources>
    <ResourceDictionary x:Key="resourcestyles">
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary /> <!-- Dummy, this is the one we will replace -->
        </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>

Then we place a ResourceDictionary in [0] (where our dummy ResourceDictionary is).

Load or replace the style dictionary (load it with the default style in Application_Startup in app.xaml.cs)

var rDictionary = new ResourceDictionary();
rDictionary.Source = new Uri(string.Format("/MyApp;component/Resources/Styles/{0}/Styles.xaml", style), UriKind.Relative);
this.Resources.MergedDictionaries[0] = rDictionary;

Replace MyApp with your applications name.