public void UpdateTiles()
        {
            GetMeData((App.Current as App).todos_Today, todayTileTextList);

            TileData frontTileData = new TileData()
            {
                TextTitle = "即将",
                TextLine1 = todayTileTextList.ElementAt(0),
                TextLine2 = todayTileTextList.ElementAt(1),
                TextLine3 = todayTileTextList.ElementAt(2)
            };

            TileBackData backTileData = new TileBackData()
            {
                TextLine1 = todayTileTextList.ElementAt(3),
                TextLine2 = todayTileTextList.ElementAt(4),
                TextLine3 = todayTileTextList.ElementAt(5)
            };

            CreateMediumTiles(frontTileData, backTileData);
            CreateLargeTiles(frontTileData, backTileData);

            ShellTile tile = ShellTile.ActiveTiles.First();

            if ((App.Current as App).flip)
            {
                var data = new FlipTileData
                {
                    Count = 0,
                    Title = "I.DO",
                    BackTitle = "I.DO",
                    BackgroundImage = new Uri("isostore:" + mediumFrontFilename, UriKind.Absolute),
                    WideBackgroundImage = new Uri("isostore:" + largeFrontFilename, UriKind.Absolute),
                    BackBackgroundImage = new Uri("isostore:" + mediumBackFilename, UriKind.Absolute),
                    WideBackBackgroundImage = new Uri("isostore:" + largeBackFilename, UriKind.Absolute)
                };

                tile.Update(data);
            }
            else
            {
                var data = new FlipTileData
                {
                    Count = 0,
                    BackTitle = String.Empty,
                    BackContent = String.Empty,
                    BackgroundImage = new Uri("isostore:" + mediumFrontFilename, UriKind.Absolute),
                    WideBackgroundImage = new Uri("isostore:" + largeFrontFilename, UriKind.Absolute),
                    BackBackgroundImage = new Uri("aa", UriKind.Relative),
                    WideBackBackgroundImage = new Uri("aa", UriKind.Relative)
                };

                tile.Update(data);
            }
        }
        private void CreateLargeTiles(TileData frontTileData, TileBackData backTileData)
        {
            LiveTileLarge largeFrontTile = new LiveTileLarge();

            largeFrontTile.Measure(new Size(691, 336));
            largeFrontTile.Arrange(new Rect(0, 0, 691, 336));

            // 准备磁贴正面图像
            largeFrontTile.DataContext = frontTileData;
            var largeFrontBmp = new WriteableBitmap(691, 336);
            largeFrontBmp.Render(largeFrontTile, null);
            largeFrontBmp.Invalidate();

            // 准备磁贴背面图像
            largeFrontTile.DataContext = backTileData;
            var largeBackBmp = new WriteableBitmap(691, 336);
            largeBackBmp.Render(largeFrontTile, null);
            largeBackBmp.Invalidate();

            var isf = IsolatedStorageFile.GetUserStoreForApplication();

            if (!isf.DirectoryExists("/Shared/ShellContent"))
            {
                isf.CreateDirectory("/Shared/ShellContent");
            }

            // 储存磁贴正面图像
            using (var stream = isf.OpenFile(largeFrontFilename, System.IO.FileMode.OpenOrCreate))
            {
                largeFrontBmp.SaveJpeg(stream, 691, 336, 0, 100);
                stream.Close();
            }

            // 储存磁贴背面图像
            using (var stream = isf.OpenFile(largeBackFilename, System.IO.FileMode.OpenOrCreate))
            {
                largeBackBmp.SaveJpeg(stream, 691, 336, 0, 100);
                stream.Close();
            }

            isf.Dispose();
        }