我创建了一个应用程序，它需要将用户数据存储在应用程序启动时创建的文件中，当我编译它时，它向我显示以下 System.IO.FileLoadException：无法找到或加载特定文件。（HRESULT中的异常：0x80131621） 和此 *System.NullReferenceException：指针 * 无效。
当应用程序启动时，它在所有操作之前调用Init()方法。

public static class FilesManager
    {

        public static StorageFolder ROOT_DIRECTORY, USER_DIRECTORY;
        public static StorageFile FILES_MANAGER_CACHE_FILE;

        public static volatile string FILES_MANAGER_CACHE;
        public static volatile StorageFolder FOLDER;

        public static async Task Init()
        {
            try
            {
                FOLDER = await ApplicationData.Current.LocalFolder.CreateFolderAsync("DashData", CreationCollisionOption.OpenIfExists);
                FOLDER = await ApplicationData.Current.LocalFolder.GetFolderAsync("DashData");
                if (FOLDER == null) Debug.WriteLine("FOLDER IS NULL.");
                FILES_MANAGER_CACHE_FILE = await FOLDER.CreateFileAsync("filesmanageruserdata.json", CreationCollisionOption.OpenIfExists);
                FILES_MANAGER_CACHE_FILE = await FOLDER.GetFileAsync("filesmanageruserdata.json");
                await LoadFilesManagerCacheAsync();
                
                Debug.WriteLine("TEXT: " + FILES_MANAGER_CACHE);
            }
            catch(Exception e)
            {
                Debug.WriteLine("ERROR: " + e.ToString());
            }
        }

        public static async Task LoadFilesManagerCacheAsync()
        {
            FILES_MANAGER_CACHE = await FileIO.ReadTextAsync(FILES_MANAGER_CACHE_FILE); 
        }
        
        public static async Task storeUserData(string content)
        {
            try
            {
                await FileIO.WriteTextAsync(FILES_MANAGER_CACHE_FILE, content);
            }catch(Exception e)
            {
                Debug.WriteLine("ERROR: " + e.ToString());
            }
        }

    }