Saving ResourceDictionary theme I have the following command bonded to my button, It's supposed detect the current used theme and change it (Dark or Light).

  var existingResourceDictionary = Application.Current.Resources.MergedDictionaries
                .Where(rd =&gt; rd.Source != null)
                .SingleOrDefault(rd =&gt; Regex.Match(rd.Source.OriginalString, @"(\/MaterialDesignThemes.Wpf;component\/Themes\/MaterialDesignTheme\.)((Light)|(Dark))").Success);

            if (existingResourceDictionary == null)
                throw new ApplicationException("Unable to find Light/Dark base theme in Application resources.");


            if (existingResourceDictionary.Source.ToString().Contains("Light"))
            {
                Settings.Default.Theme = true;
                Settings.Default.Save();
            }
            else
            {
                Settings.Default.Theme = false;
                Settings.Default.Save();
            }

            var source =
                $"pack://application:,,,/MaterialDesignThemes.Wpf;component/Themes/MaterialDesignTheme.{(Settings.Default.Theme ? "Dark" : "Light")}.xaml";
            var newResourceDictionary = new ResourceDictionary() { Source = new Uri(source) };

            Application.Current.Resources.MergedDictionaries.Remove(existingResourceDictionary);
            Application.Current.Resources.MergedDictionaries.Add(newResourceDictionary);


and in the ViewModel (when I run the application) It should detect the last changes made with the button above and apply the theme. I'm basically getting the value from the Settings that I changed above: 

   var existingResourceDictionary = Application.Current.Resources.MergedDictionaries
          .Where(rd =&gt; rd.Source != null)
          .SingleOrDefault(rd =&gt; Regex.Match(rd.Source.OriginalString, @"(\/MaterialDesignThemes.Wpf;component\/Themes\/MaterialDesignTheme\.)((Light)|(Dark))").Success);

            if (existingResourceDictionary == null)
                throw new ApplicationException("Unable to find Light/Dark base theme in Application resources.");


            var source =
                $"pack://application:,,,/MaterialDesignThemes.Wpf;component/Themes/MaterialDesignTheme.{(Settings.Default.Theme ? "Dark" : "Light")}.xaml";
            var newResourceDictionary = new ResourceDictionary() { Source = new Uri(source) };

            Application.Current.Resources.MergedDictionaries.Remove(existingResourceDictionary);
            Application.Current.Resources.MergedDictionaries.Add(newResourceDictionary);


The code is working fine but I feel like I could make it less repetitive and shorter?
You can substitute


if (existingResourceDictionary.Source.ToString().Contains("Light"))
{
    Settings.Default.Theme = true;
    Settings.Default.Save();
}
else
{
    Settings.Default.Theme = false;
    Settings.Default.Save();
}



by

Settings.Default.Theme = existingResourceDictionary.Source.ToString().Contains("Light");
Settings.Default.Save();


to shorten it a bit.