[UWP] How to change App.Current.Resources after installing Microsoft.UI.Xaml in C#?

Question

After Installing this package Microsoft.UI.Xaml

I always getting this error... and I can't change the App.Current.Resources dynamically in C#.

in my App.xaml

   xaml  
   <Application  
       x:Class="UniversalProject.UWP.App"  
       xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"  
       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"  
       xmlns:controls="using:Microsoft.UI.Xaml.Controls"  
       xmlns:local="using:UniversalProject.UWP"  
       xmlns:uwpbasic="using:UWP.Basic.Controls">  
       <Application.Resources>  
           <controls:XamlControlsResources>  
               <controls:XamlControlsResources.MergedDictionaries>  
                   <ResourceDictionary>  
                   </ResourceDictionary>  
                   <ResourceDictionary Source="Styles/ApplicationStyles.xaml" />  
               </controls:XamlControlsResources.MergedDictionaries>  
           </controls:XamlControlsResources>          
           <!--<ResourceDictionary>  
               <ResourceDictionary.MergedDictionaries>  
                   <ResourceDictionary Source="Styles/ApplicationStyles.xaml" />  
               </ResourceDictionary.MergedDictionaries>  
           </ResourceDictionary>-->  
       </Application.Resources>  
   </Application>  

Please help me to change resources dynamically in C# with Microsoft.UI.Xaml

Answer 1

Already fixed by accessing merge dictionary by index.

   xaml  
   <Application.Resources>  
           <controls:XamlControlsResources>  
               <controls:XamlControlsResources.MergedDictionaries>  
                   <ResourceDictionary>  
                       <Color x:Key="SystemAccentColor">Blue</Color>  
                   </ResourceDictionary>  
                   <ResourceDictionary Source="Styles/ApplicationStyles.xaml" />  
               </controls:XamlControlsResources.MergedDictionaries>  
           </controls:XamlControlsResources>  
       </Application.Resources>  

var r = Application.Current.Resources;
var Resources = r.MergedDictionaries[0];
Resources["SystemAccentColor"] = SystemAccentSolidColor.Color;