How to encode a file from the file system as multipart/form-data?

Question

I want to let users upload photos to Facebook in my image viewer app. As seen in this post, Facebook Graph API - upload photo using JavaScript , I have to encode my photos as multipart/form-data to be able to upload them. How to archive this encoding on Windows.Storage.StorageFile items?

Answer 1

You need to open that photo (of type Windows.Storage.StorageFile ) for reading, convert it's stream to blob, append it to FormData object and upload using whatever Ajax library you want ( WinJS.xhr , jQuery.ajax etc).

Following code illustrates it better than words:

file.openReadAsync().done(function(fileStream) {                
   var fileData = MSApp.createBlobFromRandomAccessStream(file.contentType, fileStream);
   var formData = new FormData();
   formData.append('upload', fileData, file.name);

   ... // send formData as xhr request body
});