//用于 picker 选择文件时，进行文件过滤
internal class FileExtensions{public static readonly string[] Document = new string[] { ".doc", ".xls", ".ppt", ".docx", ".xlsx", ".pptx", ".pdf", ".txt", ".rtf" };public static readonly string[] Image    = new string[] { ".jpg", ".png", ".bmp", ".gif", ".tif" };public static readonly string[] Music    = new string[] { ".mp3", ".wma", ".m4a", ".aac" };}//错误提示internal class Errors{public static readonly string NoExifThumbnail   = "No result (no EXIF thumbnail or cached thumbnail available for fast retrieval)";public static readonly string NoThumbnail       = "No result (no thumbnail could be obtained from the selected file)";public static readonly string NoAlbumArt        = "No result (no album art available for this song)";public static readonly string NoIcon            = "No result (no icon available for this document type)";public static readonly string NoImages          = "No result (no thumbnail could be obtained from the selected                                                                                 folder - make sure that the folder contains images)";public static readonly string FileGroupEmpty    = "No result (unexpected error: retrieved file group was null)";public static readonly string FileGroupLocation = "File groups are only available for library locations, please select                                                                                  a folder from one of your libraries";public static readonly string Cancel            = "No result (operation cancelled, no item selected)";}

 public static void DisplayResult(Image image, TextBlock textBlock, string thumbnailModeName,uint size, IStorageItem item, StorageItemThumbnail thumbnail, bool isGroup){// ErrorMessage.Visibility = Visibility.Collapsed;BitmapImage bitmapImage = new BitmapImage();bitmapImage.SetSource(thumbnail);image.Source = bitmapImage;textBlock.Text = String.Format("ThumbnailMode.{0}\n"+ "{1} used: {2}\n"+ "Requested size: {3}\n"+ "Returned size: {4}x{5}",thumbnailModeName,isGroup ? "Group" : item.IsOfType(StorageItemTypes.File) ? "File" : "Folder",item.Name,size,thumbnail.OriginalWidth,thumbnail.OriginalHeight);}

 <CheckBox x:Name="FastThumbnailCheckBox" ><TextBlock Text="Return fast thumbnail only (could be lower quality)" TextWrapping="Wrap" Style="{StaticResource BasicTextStyle}" /></CheckBox><ComboBox x:Name="ModeComboBox"><ComboBoxItem x:Name="PicturesView" IsSelected="true">Thumbnail for a grid layout</ComboBoxItem><ComboBoxItem x:Name="ListView">Thumbnail for a list layout</ComboBoxItem><ComboBoxItem x:Name="SingleItem">Thumbnail for a single layout</ComboBoxItem></ComboBox><Button x:Name="GetThumbnailButton" Content="Get Thumbnail" Margin="0,10,0,0" Click="GetThumbnailButton_Click"/>

   private async void GetThumbnailButton_Click(object sender, RoutedEventArgs e){// 选择图片FileOpenPicker openPicker = new FileOpenPicker();//添加图片过滤类型foreach (string extension in FileExtensions.Image){openPicker.FileTypeFilter.Add(extension);}StorageFile file = await openPicker.PickSingleFileAsync();if (file != null){string thumbnailModeName = ((ComboBoxItem)ModeComboBox.SelectedItem).Name;                 //描述缩略图的目的确定如何调整缩略图象检索。ThumbnailMode thumbnailMode = (ThumbnailMode)Enum.Parse(typeof(ThumbnailMode), thumbnailModeName);bool fastThumbnail = FastThumbnailCheckBox.IsChecked.Value;ThumbnailOptions thumbnailOptions = ThumbnailOptions.UseCurrentScale; // 默认基于显示的每英寸像素 (PPI)，增加请求的大小。if (fastThumbnail){thumbnailOptions |= ThumbnailOptions.ReturnOnlyIfCached; //仅当进行缓存或嵌入文件时检索缩略图。}const uint size = 200;                 // 针对文件检索调整的缩略图图像，这取决于缩略图的用途、要求的大小以及指定的选项。       using (StorageItemThumbnail thumbnail = await file.GetThumbnailAsync(thumbnailMode, size, thumbnailOptions)){if (thumbnail != null){// 方法在文章最开始处DisplayResult(ThumbnailImage, OutputTextBlock, thumbnailModeName, size, file, thumbnail, false);}else if (fastThumbnail){// 错误 : Errors.NoExifThumbnail
                        }else{// 错误 : Errors.NoThumbnail
                        }}}else{// 错误 : Errors.Cancel
                }}

  <Button x:Name="GetThumbnailButton"  Content="Get Thumbnail"  Click="GetThumbnailButton_Click"/>

<Image x:Name="ThumbnailImage" Stretch="None"  /><TextBlock x:Name="OutputTextBlock" />

 private async void GetThumbnailButton_Click(object sender, RoutedEventArgs e){// Pick a music fileFileOpenPicker openPicker = new FileOpenPicker();foreach (string extension in FileExtensions.Music){openPicker.FileTypeFilter.Add(extension);}StorageFile file = await openPicker.PickSingleFileAsync();if (file != null){
                    // 显示音乐文件预览。默认值，首选的大小: 小，最好至少为 40 x 40 像素长宽比: 统一，这样长宽比const ThumbnailMode thumbnailMode = ThumbnailMode.MusicView;const uint size = 100;using (StorageItemThumbnail thumbnail = await file.GetThumbnailAsync(thumbnailMode, size)){// Also verify the type is ThumbnailType.Image (album art) instead of ThumbnailType.Icon// (which may be returned as a fallback if the file does not provide album art)if (thumbnail != null && thumbnail.Type == ThumbnailType.Image){// 显示缩略图DisplayResult(ThumbnailImage, OutputTextBlock, thumbnailMode.ToString(), size, file, thumbnail, false);}else{//错误 : Errors.NoAlbumArt
                        }}}else{//错误 :  Errors.Cancel
                }}

 <Button x:Name="GetThumbnailButton"  Content="Get Thumbnail" Click="GetThumbnailButton_Click"/>

<Image x:Name="ThumbnailImage" Stretch="None"  /><TextBlock x:Name="OutputTextBlock" />

       private async void GetThumbnailButton_Click(object sender, RoutedEventArgs e){// Pick a documentFileOpenPicker openPicker = new FileOpenPicker();foreach (string extension in FileExtensions.Document){openPicker.FileTypeFilter.Add(extension);}StorageFile file = await openPicker.PickSingleFileAsync();if (file != null){                 //若要显示的文档文件的预览。默认值，首选的大小: 小，最好至少为 40 x 40 像素长宽比: 统一，这样长宽比const ThumbnailMode thumbnailMode = ThumbnailMode.DocumentsView;const uint size = 100;using (StorageItemThumbnail thumbnail = await file.GetThumbnailAsync(thumbnailMode, size)){if (thumbnail != null){DisplayResult(ThumbnailImage, OutputTextBlock, thumbnailMode.ToString(), size, file, thumbnail, false);}else{//错误 : Errors.NoIcon
                        }}}else{//错误 : Errors.Cancel
                }}

StorageFolder folder = await folderPicker.PickSingleFolderAsync();

//显示一个图片文件预览。默认值，首选的大小: 中等，最好至少为 190 x 130 像素长宽比: 统一，宽长宽比大约 .7
const ThumbnailMode thumbnailMode = ThumbnailMode.PicturesView;

<Button x:Name="GetThumbnailButton" Content="Get Thumbnail" Click="GetThumbnailButton_Click"/>

 <Image x:Name="ThumbnailImage"  Stretch="None"  /><TextBlock x:Name="OutputTextBlock" /><TextBlock x:Name="OutputDetails" />

 private async void GetThumbnailButton_Click(object sender, RoutedEventArgs e){// Pick a folderFolderPicker folderPicker = new FolderPicker();foreach (string extension in FileExtensions.Image){folderPicker.FileTypeFilter.Add(extension);}              // 显示 folderPicker 对象，以便用户可以选择文件夹。StorageFolder folder = await folderPicker.PickSingleFolderAsync();if (folder != null){                  //描述用于在查询结果中分组文件的条件，并确定来自子文件夹的文件是否包含在结果中。const CommonFolderQuery monthShape = CommonFolderQuery.GroupByMonth;//基于每个文件的 System.ItemDate 属性按月份生成虚拟文件夹。// Verify queries are supported because they are not supported in all picked locations.
                 //检索指示当前文件夹是否支持指定公共文件夹查询的值。if (folder.IsCommonFolderQuerySupported(monthShape)){// Convert folder to file group and query for items                     // 创建用于执行针对当前文件夹的子存储文件夹的筛选搜索查询的对象。根据所指定的文件夹属性，分组搜索结果。IReadOnlyList<StorageFolder> months = await folder.CreateFolderQuery(monthShape).GetFoldersAsync();if (months != null && months.Count > 0){const ThumbnailMode thumbnailMode = ThumbnailMode.PicturesView;const uint size = 200;StorageFolder firstMonth = months[0];using (StorageItemThumbnail thumbnail = await firstMonth.GetThumbnailAsync(thumbnailMode, size)){if (thumbnail != null){DisplayResult(ThumbnailImage, OutputTextBlock, thumbnailMode.ToString(), size, firstMonth, thumbnail, true);// Also display the hierarchy of the file group to better visualize where the thumbnail comes from
                                // 基于通用文件查询获取当前文件夹中的文件。IReadOnlyList<StorageFile> files = await firstMonth.GetFilesAsync();  if (files != null){StringBuilder output = new StringBuilder("\nList of files in this group:\n\n");foreach (StorageFile file in files){output.AppendFormat("{0}\n", file.Name);}OutputDetails.Text = output.ToString();}}else{//错误 : Errors.NoImages
                                }}}else{//错误 : Errors.FileGroupEmpty
                        }}else{//错误 :  Errors.FileGroupLocation,
                    }}else{//错误 : Errors.Cancel
                }}