2

我正在尝试序列化 ObservableCollection。但我收到以下错误：让我知道如何解决这个问题？

错误：

{System.InvalidOperationException：在 f:\TFS\New TFS\PDFReader\Posh.PdfReader.Win8\eText\Common\ApplicationSettings.cs:line 中出现反映类型 'System.Collections.ObjectModel.ObservableCollection 1.MoveNext() 的错误16 --- 从先前引发异常的位置结束堆栈跟踪 --- 在 System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 在 System.Runtime .CompilerServices.TaskAwaiter.GetResult() 在 eText.ViewModel.MainViewModel.d__a.MoveNext() 在 f:\TFS\New TFS\PDFReader\Posh.PdfReader.Win8\eText\ViewModel\MainViewModel.cs:line 268}1[eText.DataModel.BooksDownloadedData]'. ---> System.InvalidOperationException: There was an error reflecting type 'eText.DataModel.BooksDownloadedData'. ---> System.InvalidOperationException: Cannot serialize member 'eText.DataModel.BooksDownloadedData.DownloadedBookFileDetails' of type 'Windows.Storage.StorageFile', see inner exception for more details. ---> System.InvalidOperationException: Windows.Storage.StorageFile cannot be serialized because it does not have a parameterless constructor. --- End of inner exception stack trace --- at System.Xml.Serialization.StructModel.CheckSupportedMember(TypeDesc typeDesc, MemberInfo member, Type type) at System.Xml.Serialization.StructModel.GetPropertyModel(PropertyInfo propertyInfo) at System.Xml.Serialization.StructModel.GetFieldModel(MemberInfo memberInfo) at System.Xml.Serialization.XmlReflectionImporter.InitializeStructMembers(StructMapping mapping, StructModel model, Boolean openModel, String typeName, RecursionLimiter limiter) at System.Xml.Serialization.XmlReflectionImporter.ImportStructLikeMapping(StructModel model, String ns, Boolean openModel, XmlAttributes a, RecursionLimiter limiter) at System.Xml.Serialization.XmlReflectionImporter.ImportTypeMapping(TypeModel model, String ns, ImportContext context, String dataType, XmlAttributes a, Boolean repeats, Boolean openModel, RecursionLimiter limiter) --- End of inner exception stack trace --- at System.Xml.Serialization.XmlReflectionImporter.ImportTypeMapping(TypeModel model, String ns, ImportContext context, String dataType, XmlAttributes a, Boolean repeats, Boolean openModel, RecursionLimiter limiter) at System.Xml.Serialization.XmlReflectionImporter.CreateArrayElementsFromAttributes(ArrayMapping arrayMapping, XmlArrayItemAttributes attributes, Type arrayElementType, String arrayElementNs, RecursionLimiter limiter)
at System.Xml.Serialization.XmlReflectionImporter.ImportArrayLikeMapping(ArrayModel model, String ns, RecursionLimiter limiter) at System.Xml.Serialization.XmlReflectionImporter.ImportTypeMapping(TypeModel model, String ns, ImportContext context, String dataType, XmlAttributes a, Boolean repeats, Boolean openModel, RecursionLimiter limiter) --- End of inner exception stack trace --- at System.Xml.Serialization.XmlReflectionImporter.ImportTypeMapping(TypeModel model, String ns, ImportContext context, String dataType, XmlAttributes a, Boolean repeats, Boolean openModel, RecursionLimiter limiter) at System.Xml.Serialization.XmlReflectionImporter.ImportElement(TypeModel model, XmlRootAttribute root, String defaultNamespace, RecursionLimiter limiter) at System.Xml.Serialization.XmlReflectionImporter.ImportTypeMapping(Type type, XmlRootAttribute root, String defaultNamespace) at System.Xml.Serialization.XmlSerializer..ctor(Type type, String defaultNamespace) at System.Xml.Serialization.XmlSerializer..ctor(Type type) at eText.Common.Xml.Serialize[T](Object obj, Type[] extraTypes) in f:\TFS\New TFS\PDFReader\Posh.PdfReader.Win8\eText\Common\Utility.cs:line 81
at eText.Common.ApplicationSettings.<SaveDataToFileAsync>d__0

我用来序列化的代码：

书类：

[DataContract] 
public class Book : ViewModelBase
{
    #region Constructor

    /// <summary>
    /// Initializes a new instance of the <see cref="Book" /> class.
    /// </summary>
    public Book(){}

    /// <summary>
    /// Initializes a new instance of the <see cref="Book" /> class.
    /// </summary>
    /// <param name="BookTitle">The book title.</param>
    /// <param name="BookCategory">The book category.</param>
    /// <param name="DownloadURL">The download URL.</param>
    /// <param name="TotalNumberOfPages">The total number of pages.</param>
    /// <param name="BookAuthor">The book author.</param>
    /// <param name="ImageURL">The image URL.</param>
    public Book(string BookTitle,string BookCategory,string DownloadURL, string TotalNumberOfPages, string BookAuthor, string ImageURL)
    {
        this.BookCategory = BookCategory;
        this.BookTitle = BookTitle;
        this.BookAuthor = BookAuthor;
        this.TotalNumberOfPages = TotalNumberOfPages;
        this.DownloadURL = DownloadURL;
        this.ImageURL = ImageURL;
    }

    #endregion    
}

BooksDownloadedData 类

 /// <summary>
    /// Class to store downloaded books metaData
    /// </summary>
    [DataContract] 
    public class BooksDownloadedData
    {

        /// <summary>
        /// The downloaded books detail
        /// </summary>
        [DataMember]
        public Book DownloadedBooks { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether this instance is downloaded completed.
        /// </summary>
        /// <value>
        /// <c>true</c> if this instance is downloaded completed; otherwise, <c>false</c>.
        /// </value>
       [DataMember]
        public bool IsDownloadedCompleted { get; set; }
}

为 BooksDownloadedData 创建了一个 ObservableCollection，然后在序列化后将其保存在本地存储中，但在序列化时出现错误：

// Create object to get the saved meta data of files
  ObservableCollection<BooksDownloadedData> downLoadedFiles;

 // Save the data to the local storage
                await ApplicationSettings.SaveDataToFileAsync<ObservableCollection<BooksDownloadedData>>(fileName, downLoadedFiles);

 public static async Task SaveDataToFileAsync<T>(string key, T value, bool roaming = false, Type[] extraTypes = null)
        {
            var file = roaming ? await ApplicationData.Current.RoamingFolder.CreateFileAsync(key + ".xml", CreationCollisionOption.ReplaceExisting) :
                await ApplicationData.Current.LocalFolder.CreateFileAsync(key + ".xml", CreationCollisionOption.ReplaceExisting);

            var xml = Xml.Serialize<T>(value, extraTypes);
            await FileIO.WriteTextAsync(file, xml, UnicodeEncoding.Utf8);
        }

 public static string Serialize<T>(object obj, Type[] extraTypes = null)
        {
            using (var sw = new StringWriter())
            {
                var serializer = extraTypes == null ? new XmlSerializer(typeof(T)) : new XmlSerializer(typeof(T), extraTypes);
                serializer.Serialize(sw, obj);
                return sw.ToString();
            }
        }
4

2 回答 2

3

从您的堆栈跟踪中，我看到：

Cannot serialize member 'eText.DataModel.BooksDownloadedData.DownloadedBookFileDetails' of type 'Windows.Storage.StorageFile', see inner exception for more details. ---> System.InvalidOperationException: Windows.Storage.StorageFile cannot be serialized because it does not have a parameterless constructor.

该类的限制之一XmlSerializer是被序列化的类必须具有无参数构造函数。

你可以使用DataContractSerializer代替吗？

于 2013-01-24T09:00:45.800 回答
2

问题在于使用Windows.Storage.StorageFile，这显然不是为了与序列化很好地配合（或至少：不是XmlSerializer）。

您也许可以重构您的模型，这样您就不需要使用StorageFile. 您也许可以用 标记该成员 ( DownloadedBookFileDetails) ，并在反序列化后手动[XmlIgnore]重新创建。StorageFile您也许可以使用不同的序列化程序（DataContractSerializer、JSON.NET、protobuf-net 等）。

然而！在大多数情况下，我看到（并且我经常处理序列化）人们犯的关键错误是试图与序列化器作斗争，以便他们可以继续使用现有的域模型。实际上，最简单的做法通常是：创建一个 DTO：一个单独的模型，专门用于将数据表示为序列化的桥梁，然后映射到/从 DTO 模型和您的主域模型。

这不仅每次都非常容易工作，而且如果你想的话，它也会让你处于一个非常有利的位置：

  • 在不影响序列化数据的情况下修改域模型（您只需调整映射）
  • 添加具有不同布局的单独版本/ API（可能是公共 API 与私有 API）
  • 使用不同的序列化程序（另外或代替）
于 2013-01-24T09:06:37.137 回答