c# - Image to string -


i have news list, contain thumbnails:

example

i'm getting json server, means pictures - links

my code inserting pictures:

foreach (article article in newslist.result.articles) {     newslistboxitem nlbi = new newslistboxitem();     nlbi.title.text = article.title;     nlbi.date.text = us.unixdatetonormal(article.date.tostring());     nlbi.id.text = article.id.tostring();     if (article.imageurl != null)     {         bitmapimage image = new bitmapimage(new uri(article.imageurl));         nlbi.thumbnail.source = image;     }     newslistbox.items.add(nlbi); }

if enter application in offline mode - wont show up, need save them, prefered method - string!

which means need convert them base64:

bitmapimage image = new bitmapimage(new uri(article.imageurl)); byte[] bytearray = null; using (memorystream ms = new memorystream()) {     writeablebitmap wbitmp = new writeablebitmap(image );     wbitmp .savejpeg(ms, wbitmp.pixelwidth, wbitmp.pixelheight, 0, 100);     ms.seek(0, seekorigin.begin);     bytearray = ms.getbuffer(); } string str = convert.tobase64string(bytearray);

code fails nullreferenceexception mistake? code fails on line:

writeablebitmap wbitmp = new writeablebitmap(image);

error:

an exception of type 'system.nullreferenceexception' occurred in system.windows.ni.dll not handled in user code

i tried use image project: 

bitmapimage image = new bitmapimage(new uri("theme/menubutton.png",urikind.relative));

but still fails nullref - know image exists, if nul wouldn't see in imagebox

the problem image needs loaded. can try saving image first timem shown:

foreach (article article in newslist.result.articles) {     newslistboxitem nlbi = new newslistboxitem();     nlbi.title.text = article.title;     nlbi.date.text = us.unixdatetonormal(article.date.tostring());     nlbi.id.text = article.id.tostring();     if (article.imageurl != null)     {         bitmapimage image = new bitmapimage(new uri(article.imageurl));         image.imageopened += (s, e) =>             {                 byte[] bytearray = null;                 using (memorystream ms = new memorystream())                 {                     writeablebitmap wbitmp = new writeablebitmap(image );                     wbitmp .savejpeg(ms, wbitmp.pixelwidth, wbitmp.pixelheight, 0, 100);                     bytearray = ms.toarray();                 }                 string str = convert.tobase64string(bytearray);             };         nlbi.thumbnail.source = image;     }     newslistbox.items.add(nlbi); }

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