我收到这个错误
错误 6 可访问性不一致：返回类型“HomePage.Models.SaveResult”比方法“HomePage.Models.CarDataStore.SaveFillup(HomePage.Models.Fillup, System.Action)”更难访问
这是课程：
private const string CAR_PHOTO_DIR_NAME = "FuelTracker";
private const string CAR_PHOTO_FILE_NAME = "CarPhoto.jpg";
private const string CAR_PHOTO_TEMP_FILE_NAME = "TempCarPhoto.jpg";
private const string CAR_KEY = "FuelTracker.Car";
private static readonly IsolatedStorageSettings appSettings =
IsolatedStorageSettings.ApplicationSettings;
private static Car _car;
public static event EventHandler CarUpdated;
/// <summary>
/// Gets or sets the car data, loading the data from isolated storage
/// (if there is any saved data) on the first access.
/// </summary>
public static Car Car
{
get
{
if (_car == null)
{
if (appSettings.Contains(CAR_KEY))
{
_car = (Car)appSettings[CAR_KEY];
_car.Picture = GetCarPhoto(CAR_PHOTO_FILE_NAME);
}
else
{
_car = new Car
{
FillupHistory = new ObservableCollection<Fillup>()
};
}
}
return _car;
}
set
{
_car = value;
NotifyCarUpdated();
}
}
/// <summary>
/// Saves the car data to isolated storage.
/// </summary>
/// <param name="errorCallback">The action to execute if the
/// storage attempt fails.</param>
public static void SaveCar(Action errorCallback)
{
try
{
appSettings[CAR_KEY] = Car;
appSettings.Save();
DeleteTempCarPhoto();
SaveCarPhoto(CAR_PHOTO_FILE_NAME, Car.Picture, errorCallback);
NotifyCarUpdated();
}
catch (IsolatedStorageException)
{
errorCallback();
}
}
/// <summary>
/// Deletes the car data from isolated storage and resets the Car property.
/// </summary>
public static void DeleteCar()
{
appSettings.Remove(CAR_KEY);
appSettings.Save();
Car = null;
DeleteCarPhoto();
DeleteTempCarPhoto();
NotifyCarUpdated();
}
/// <summary>
/// Gets the temporary car photo from isolated storage.
/// </summary>
/// <returns>The temporary car photo.</returns>
public static BitmapImage GetTempCarPhoto()
{
return GetCarPhoto(CAR_PHOTO_TEMP_FILE_NAME);
}
/// <summary>
/// Saves the temporary car photo to isolated storage.
/// </summary>
/// <param name="carPicture">The image to save.</param>
/// <param name="errorCallback">The action to execute if the storage
/// attempt fails.</param>
public static void SaveTempCarPhoto(BitmapImage carPicture,
Action errorCallback)
{
SaveCarPhoto(CAR_PHOTO_TEMP_FILE_NAME, carPicture, errorCallback);
}
/// <summary>
/// Deletes the car photo from isolated storage.
/// </summary>
private static void DeleteCarPhoto()
{
DeletePhoto(CAR_PHOTO_FILE_NAME);
}
/// <summary>
/// Deletes the temporary car photo from isolated storage.
/// </summary>
public static void DeleteTempCarPhoto()
{
DeletePhoto(CAR_PHOTO_TEMP_FILE_NAME);
}
/// <summary>
/// Deletes the photo with the specified file name.
/// </summary>
/// <param name="fileName">The name of the photo file to delete.</param>
private static void DeletePhoto(String fileName)
{
using (var store = IsolatedStorageFile.GetUserStoreForApplication())
{
var path = Path.Combine(CAR_PHOTO_DIR_NAME, fileName);
if (store.FileExists(path)) store.DeleteFile(path);
}
}
/// <summary>
/// Gets the specified car photo from isolated storage.
/// </summary>
/// <param name="fileName">The filename of the photo to get.</param>
/// <returns>The requested photo.</returns>
private static BitmapImage GetCarPhoto(string fileName)
{
using (var store = IsolatedStorageFile.GetUserStoreForApplication())
{
string path = Path.Combine(CAR_PHOTO_DIR_NAME, fileName);
if (!store.FileExists(path)) return null;
using (var stream = store.OpenFile(path, FileMode.Open))
{
var image = new BitmapImage();
image.SetSource(stream);
return image;
}
}
}
/// <summary>
/// Saves the specified car photo to isolated storage using the
/// specified filename.
/// </summary>
/// <param name="fileName">The filename to use.</param>
/// <param name="carPicture">The image to save.</param>
/// <param name="errorCallback">The action to execute if the storage
/// attempt fails.</param>
private static void SaveCarPhoto(string fileName, BitmapImage carPicture,
Action errorCallback)
{
if (carPicture == null) return;
try
{
using (var store = IsolatedStorageFile.GetUserStoreForApplication())
{
var bitmap = new WriteableBitmap(carPicture);
var path = Path.Combine(CAR_PHOTO_DIR_NAME, fileName);
if (!store.DirectoryExists(CAR_PHOTO_DIR_NAME))
{
store.CreateDirectory(CAR_PHOTO_DIR_NAME);
}
using (var stream = store.OpenFile(path, FileMode.Create))
{
bitmap.SaveJpeg(stream, bitmap.PixelWidth, bitmap.PixelHeight, 0, 100);
}
}
}
catch (IsolatedStorageException)
{
errorCallback();
}
}
/// <summary>
/// Validates the specified Fillup and then, if it is valid, adds it to
/// Car.FillupHistory collection.
/// </summary>
/// <param name="fillup">The fill-up to save.</param>
/// <param name="errorCallback">The action to execute if the storage
/// attempt fails.</param>
/// <returns>The validation results.</returns>
public static SaveResult SaveFillup(Fillup fillup, Action errorCallback)
{
var lastReading =
Car.FillupHistory.Count > 0 ?
Car.FillupHistory.First().OdometerReading :
Car.InitialOdometerReading;
fillup.DistanceDriven = fillup.OdometerReading - lastReading;
var saveResult = new SaveResult();
var validationResults = fillup.Validate();
if (validationResults.Count > 0)
{
saveResult.SaveSuccessful = false;
saveResult.ErrorMessages = validationResults;
}
else
{
Car.FillupHistory.Insert(0, fillup);
saveResult.SaveSuccessful = true;
SaveCar(delegate {
saveResult.SaveSuccessful = false;
errorCallback(); });
}
return saveResult;
}
private static void NotifyCarUpdated()
{
var handler = CarUpdated;
if (handler != null) handler(null, null);
}
}