从可观察集合中删除项会使 XML 序列化更新失败

Question

我使用可观察集合在我的应用程序中保存列表，并使用 XML 将该列表保存到独立存储。 当我添加项目时，该应用程序正常，但是当我删除项目并重新启动应用程序时，它无法读取 XML。我使用 i 工具从独立存储中获取该 XML，是的，它的结构是错误的。

这是代码

public void saveToXML()
        {
            IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForApplication();                       
            XmlWriterSettings xmlWriterSetting = new XmlWriterSettings();
            xmlWriterSetting.Indent = true;
            using (storage)
            {
                using (IsolatedStorageFileStream fsIdea = new IsolatedStorageFileStream("Idea.xml", FileMode.OpenOrCreate, storage))
                {
                    using (XmlWriter xWIdea = XmlWriter.Create(fsIdea, xmlWriterSetting))
                    {
                        XmlSerializer xSIdea = new XmlSerializer(typeof(ObservableCollection<IdeaViewModel>));
                        xSIdea.Serialize(xWIdea, App.ViewModel.ItemsIdea);
                    }
                }                
            }
        }
        public void readFromXML()
        {
            IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForApplication();
            if (!storage.FileExists("Idea.xml") )
            {
                saveToXML();
            }
            using (storage)
            {
                using (IsolatedStorageFileStream fsIdea = new IsolatedStorageFileStream("Idea.xml", FileMode.Open, storage))
                {
                    XmlSerializer xSIdea = new XmlSerializer(typeof(ObservableCollection<IdeaViewModel>));
                    App.ViewModel.ItemsIdea = xSIdea.Deserialize(fsIdea) as ObservableCollection<IdeaViewModel>;
                }                
            }
        }

当我删除项目并重新启动应用程序时，这是错误的XML文件，错误在第9行，看起来XML文件仍然保留已删除项目的一部分？

<?xml version="1.0" encoding="utf-8"?>
<ArrayOfIdeaViewModel xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <IdeaViewModel>
    <IdeaContent>sdfsd</IdeaContent>
  </IdeaViewModel>
  <IdeaViewModel>
    <IdeaContent>sdfds</IdeaContent>
  </IdeaViewModel>
</ArrayOfIdeaViewModel>aContent>sf</IdeaContent>
  </IdeaViewModel>
  <IdeaViewModel>
    <IdeaContent>sdfsd</IdeaContent>
  </IdeaViewModel>
  <IdeaViewModel>
    <IdeaContent>sdfds</IdeaContent>
  </IdeaViewModel>
</ArrayOfIdeaViewModel>

（我把readFromXML（）放在app的构造函数中，saveToXML（）放在这里

// Code to execute when the application is deactivated (sent to background)
    // This code will not execute when the application is closing
    private void Application_Deactivated(object sender, DeactivatedEventArgs e)
    {
        saveToXML();                     
    }
    // Code to execute when the application is closing (eg, user hit Back)
    // This code will not execute when the application is deactivated
    private void Application_Closing(object sender, ClosingEventArgs e)
    {
        // Ensure that required application state is persisted here.
        saveToXML();            
    }

Answer 1

保存时，请使用 FileMode.Create 而不是 FileMode.OpenOrCreate：

using (IsolatedStorageFileStream fsIdea = new IsolatedStorageFileStream("Idea.xml", FileMode.Create, storage))

在您的情况下，您只是在编辑文件的旧版本，因此您可能有一些工件。