c# - Save a custom class to Isolated Storage using a Collection

Question

I have created a custom class named ImageItem which contains a BitmapImage and string to gather the response of the CaptureImageTask. I would like to save each image and its respective path to an ObservableCollection which is bound to a listbox in my view.

As of now the listbox populates correctly, but I am having trouble storing ObservableCollection<ImageItem> in isolated storage, I believe because of the BitmapImage type.

I am not sure of how to fix my solution so that the BitmapImage will be allowed to be saved to isolated storage along with its respective path within an ObservableCollection.

I believe I have narrowed down the issue to BitmapImage not being a serializable type. I have tried using [DataContract] and '[DataMember]attributes withinImageItem.cs` without success. I have never attempted to save a nonprimitive type.

Following are the code, with some description of each file.

• ImageItem.cs

  public class ImageItem
  {
      public BitmapImage ImageUri
      {
          get;
          set;
      }
  
      public string ImagePath
      {
          get;
          set;
      }
  }
  

• Settings.cs

  I am using a Settings class to create the ObservableCollection of custom type.

  public static class Settings
  {
      public static readonly Setting<ObservableCollection<ImageItem>> imageList = new Setting<ObservableCollection<ImageItem>>("imageList", new ObservableCollection<ImageItem>());
  }
  

• Setting.cs

  Where Setting is a class that reads and saves data to Isolated Storage

  public class Setting<T>
  {
      string name;
      T value;
      T defaultValue;
      bool hasValue;
  
      public Setting(string name, T defaultValue)
      {
          this.name = name;
          this.defaultValue = defaultValue;
      }
  
      public T Value
      {
          get
          {
              //Check for the cached value
              if (!this.hasValue)
              {
                  //Try to get the value from Isolated Storage
                  if (!IsolatedStorageSettings.ApplicationSettings.TryGetValue(this.name, out this.value))
                  {
                      //It hasn't been set yet
                      this.value = this.defaultValue;
                      IsolatedStorageSettings.ApplicationSettings[this.name] = this.value;
                  }
                  this.hasValue = true;
              }
              return this.value;
          }
  
          set
          {
              //Save the value to Isolated Storage
              IsolatedStorageSettings.ApplicationSettings[this.name] = value;
              this.value = value;
              this.hasValue = true;
          }
      }
  
      public T DefaultValue
      {
          get { return this.defaultValue; }
      }
  
      // Clear cached value
      public void ForceRefresh()
      {
          this.hasValue = false;
      }
  }
  

• MainPage.xaml.cs

  From here I am simply attempting to save the result of the CameraCaptureTask which is used to populate the ObservableCollection and the listbox

  void cameraCaptureTask_Completed(object sender, PhotoResult e)
  {
      if (e.TaskResult == TaskResult.OK)
      {
          //values declared earlier
          imgChosenPhotoFilePath = null;
          bmp = new BitmapImage();
  
          imgChosenPhotoFilePath = e.OriginalFileName;
  
          bmp.SetSource(e.ChosenPhoto);
          imgChosenPhoto.Source = bmp;
  
          //Add photo to listbox and observablecollection
          AddToImgList(imgChosenPhotoFilePath, bmp);
      }
  }
  
  private void AddToImgList(string filePath, BitmapImage bitmap)
  {
      //save the values to the ObservableCollection
      Settings.imageList.Value.Add(new ImageItem() { ImagePath = filePath, ImageUri = bitmap });
  
      //populate the listbox in the view named imgList
      imgList.ItemsSource = Settings.imageList.Value;
  }
  

Answer 1

正如您所发现的，您无法序列化BitmapImage. 最简单的替代方法是将其保存为单独的文件，然后将文件名保存在您正在序列化的集合中。

显然，在反序列化时，您需要从磁盘读取文件并将其加载回 BitmapImage。

如果您要在应用程序的整个生命周期中保留这些数据以供使用，那么将图像直接保存到 IsolatedStorage 并将路径保留在视图模型中可能会更容易。然后，您可以将路径绑定到 ListBoxItemTemplate 中的图像。