DirectoryCreator/ThemeManager.cs

using System.Windows;

namespace DirectoryCreator
{
    public static class ThemeManager
    {
        private static readonly Uri DarkThemeUri = new Uri("/Themes/DarkTheme.xaml", UriKind.Relative);
        private static readonly Uri LightThemeUri = new Uri("/Themes/LightTheme.xaml", UriKind.Relative);

        public static void SetTheme(bool isDarkTheme)
        {
            var app = Application.Current;
            if (app == null) return;

            var mergedDicts = app.Resources.MergedDictionaries;

            // Buscar y eliminar los temas existentes
            ResourceDictionary themeToRemove = null;
            foreach (ResourceDictionary dict in mergedDicts)
            {
                if (dict.Source != null && (dict.Source.OriginalString.Contains("LightTheme") || dict.Source.OriginalString.Contains("DarkTheme")))
                {
                    themeToRemove = dict;
                    break;
                }
            }

            if (themeToRemove != null)
            {
                mergedDicts.Remove(themeToRemove);
            }

            // Agregar el nuevo tema
            mergedDicts.Add(new ResourceDictionary
            {
                Source = isDarkTheme ? DarkThemeUri : LightThemeUri
            });
        }
    }
}