void change(string resourceName)
        {
            var resourceDict = new ResourceDictionary() { Source = new Uri($"pack://application:,,,/WPF中英文切換;component/languages/{resourceName}.xaml") };

            var allLanguageDicts =
                Application.Current.Resources.MergedDictionaries.Where(x 
 
=>
                    x.Source.OriginalString.Contains("languages")).ToList();
            if (!allLanguageDicts.Exists(x => x.Source.OriginalString.Contains(resourceName)))
            {
                Application.Current.Resources.MergedDictionaries.Add(resourceDict);
            }
            
 
for (int i = allLanguageDicts.Count() - 1; i > 0; i--)
            {
                var dict = allLanguageDicts[i];
                if (dict.Source.OriginalString != resourceDict.Source.OriginalString)
                {
                    Application.Current.Resources.MergedDictionaries.Remove(dict);
                }
            }
        }
 

原始碼：https://files.cnblogs.com/files/lizhijian/20201215WPF%E4%B8%AD%E8%8B%B1%E6%96%87%E5%88%87%E6%8D%A2.zip