MARKUS

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows.Media.Imaging;

namespace PageManager

{

    public class PageStorage

    {

        List<PageItem> fileItems = new List<PageItem>();

        string _localStorage;

        string _BaseUri;

        BitmapFrame PageImage;

        public PageStorage(string BaseUri, string localStoragePath)

        {

            try

            {

                _BaseUri = BaseUri;

                _localStorage = localStoragePath;

                System.IO.Directory.CreateDirectory(_localStorage);

                //GetPageAsync(1).ConfigureAwait(false);

            }

            catch (Exception ex)

            {

                throw new Exception("PageStorage", ex);

            }

        }

        public void ResetImage()

        {

            if (PageImage != null)

            {

                PageImage.UriSource = null;

                PageImage = null;

            }

            //PageImage.CreateOptions = BitmapCreateOptions.IgnoreImageCache;

        }

        public async Task<BitmapFrame> GetPageAsync(int PageNo)

        {

            try

            { = BitmapFrame.Create(new Uri(), BitmapCreateOptions.None, BitmapCacheOption.OnLoad);

                ResetImage();

                PageImage = new BitmapImage

                {

                    CacheOption = BitmapCacheOption.OnDemand,

                    CreateOptions = BitmapCreateOptions.IgnoreImageCache

                };

                var page = fileItems.Where(x => x.PageNo == PageNo);

                PageImage.BeginInit();

                if (page.Count() > 0)

                {

                    PageImage.UriSource = page.First().LocalUri;

                }

                else

                {

                    string downloadFilePath = System.IO.Path.Combine(_localStorage,PageNo.ToString() + ".png");

                    PageItem item = new PageItem

                    {

                        PageNo = PageNo,

                        OriginalUri = new Uri(_BaseUri.Replace("{PageNo}", PageNo.ToString())),

                        LocalUri = new Uri(downloadFilePath, UriKind.Absolute),

                        LocalFilePath = downloadFilePath

                    };

                    fileItems.Add(item);

                    using (System.Net.WebClient client = new System.Net.WebClient())

                    {

                        client.UseDefaultCredentials = true;

                        var task = client.DownloadFileTaskAsync(item.OriginalUri, downloadFilePath);

                        client.DownloadFileCompleted += (snd, evt) =>

                        {

                            item.IsDownLoad = true;

                        };

                        await task;

                    }

                    PageImage.UriSource = item.LocalUri;

                }

               PageImage.EndInit();

            }

            catch (Exception ex)

            {

                throw new Exception("GetPageAsync(string BasePageUri,int PageNo)", ex);

            }

            finally

            {

                GC.Collect(2);

                GC.Collect(2);

            }

            return PageImage;

        }

        public void Clear()

        {

            try

            {

                ResetImage();

            }

            catch (Exception ex)

            {

                System.Diagnostics.Debug.WriteLine(ex.ToString());

            }

            try

            {

                fileItems.ForEach(x =>

                {

                    System.IO.File.Delete(x.LocalFilePath);

                });

                System.IO.Directory.Delete(_localStorage, true);

            }

            catch (Exception ex)

            {

                System.Diagnostics.Debug.WriteLine(ex.ToString());

            }

        }

    }

}