Exception in BackgroundUploader

Question

I am trying to upload some avi file to server. It works fine with HttpRequest but i need to continue uploading even if i suspend app so thats why i am trying to use BackgroundUploader. I am following this guideline on msdn http://msdn.microsoft.com/en-us/library/windows/apps/jj152727.aspx. So my code looks something like this.

StorageFile storageFile = KnownFolders.VideosLibrary.GetFileAsync("fileName");
BackgroundUploader uploader = new BackgroundUploader();
uploader.Method = "POST";
uploader.SetRequestHeader("Content-Type", "multipart/form-data; boundary=" + boundary);
var fs = await storageFile.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite);
IInputStream aaaa = fs.GetInputStreamAt(0);

UploadOperation upload = uploader.CreateUploadFromStreamAsync(new Uri("uploadUri"), aaaa);

await HandleUploadAsync(upload, true);

the rest is same as on MSDN. And i am getting exception Unsupported media type (415) in method HandleUploadAsync on line

await upload.StartAsync().AsTask(cts.Token, progressCallback);

What am i doing wrong? Or what can cause this kind of exception?

EDIT : I solved my problem as i commented down here and in my answer. I think at the end i am basically just sending some data to server that are recognized and interpreted as i want to. So if i use BackgroundUploader i am not only uploading some file i am also sending information about how am i doing that(as i mentioned in my answer). So by the same idea i can also upload folder to server and by that i am not sending any actual content only some description about how to do that. And if i compare request that i am making by HttpRequest and BackgroundUploader they are equal and thats what i wanted.

Answer 1

So the problem part was the header of request. I have some header in my request that is recognized by server and i was trying to put it to BackgroundUploader through SetRequestheader method but it did not work. As Kieqic suggested i used Fiddler and by that i compare request made by HttpRequest and BackgroundUploader. I found out they are completely different. So through SetRequestheader i add some parts like expected Content-Type and for the rest parts of header to make them equal i add it before content of my file as array of bytes. And this works so conclusion is in my case using Fiddler that helped my how to construct request header.