c# - Read Barcode in an WP8.1 app with ZXing -

im writing first app wp8.1. app need scan barcode.

        public async void scanbarcodeasync(windows.storage.storagefile afile)     {         writeablebitmap bitmap;         bitmapdecoder decoder;          using (irandomaccessstream str = await afile.openreadasync())         {             decoder = await bitmapdecoder.createasync(str);             bitmap = new writeablebitmap(convert.toint32(decoder.pixelwidth),                                          convert.toint32(decoder.pixelheight));             await bitmap.setsourceasync(str);         }          zxing.barcodereader reader = new barcodereader();         /*reader.options.possibleformats = new zxing.barcodeformat[]         {             zxing.barcodeformat.code_128,             zxing.barcodeformat.code_39         };*/         reader.options.tryharder = true;         reader.autorotate = true;          var results = reader.decode(bitmap);         if (results != null)         {             edtbarcode.text = results.text;          }         else         {             edtbarcode.text = "error";         }     } 

the file method created way

    async void startcapture()     {         var cameraid = await getcameraid(windows.devices.enumeration.panel.back);          mediacaptureinitializationsettings settings = new mediacaptureinitializationsettings();         settings.photocapturesource = windows.media.capture.photocapturesource.videopreview;         settings.streamingcapturemode = windows.media.capture.streamingcapturemode.video;         settings.audiodeviceid = string.empty;         settings.videodeviceid = cameraid.id;          capturemanager = new mediacapture();    //define mediacapture object           await capturemanager.initializeasync(settings);   //initialize mediacapture ,          var focussettings = new focussettings();         focussettings.autofocusrange = autofocusrange.macro;         focussettings.mode = focusmode.auto;         focussettings.waitforfocus = true;         focussettings.disabledriverfallback = false;          capturemanager.videodevicecontroller.focuscontrol.configure(focussettings);         capturemanager.setpreviewrotation(videorotation.clockwise90degrees);         capturepreview.source = capturemanager;   //start preiving on captureelement              await capturemanager.startpreviewasync();  //start camera capturing        }     async private void capture_photo_click(object sender, routedeventargs e)     {         //create jpeg image encoding format storing image in jpeg type           imageencodingproperties imgformat = imageencodingproperties.createjpeg();         // create storage file in local app storage           if (imageindex > 0)         {             storagefile delfile = await applicationdata.current.localfolder.getfileasync("photo" + convert.tostring(imageindex - 1) + ".jpg");             await delfile.deleteasync();         }         file = await applicationdata.current.localfolder.createfileasync("photo" + convert.tostring(imageindex++) + ".jpg", creationcollisionoption.replaceexisting);         // take photo , store on file location.           await capturemanager.capturephototostoragefileasync(imgformat, file);         //// create storage file in picture library           //storagefile file = await knownfolders.pictureslibrary.createfileasync("photo.jpg",creationcollisionoption.generateuniquename);           // photo bitmapimage using storage file path.            bmpimage = new bitmapimage();         bmpimage.createoptions = bitmapcreateoptions.none;         bmpimage.urisource = new uri(file.path);          imagetaken = true;         frame.navigate(typeof(mainpage));         frame.navigate(typeof(mainpage));     } 

i dont error running code. result zxing null. scanbarcodeasync-function directly run after taking picture. image app takes not sharp. can cause problem?

im happy suggestions solve problem.