c# - Asynchronous download algorithm with progress value -

i made simple algorithm winrt app. having stream of class webresponse. need download file asynchronously "progresschanged" event. here method:

public async void downloadfileasync(string uri, storagefile path) {         var request = webrequest.createhttp(uri);         var response = await request.getresponseasync();         if (response != null)         {             long totalbytes = response.contentlength;             long writedbytes = 0;             using(var webstream = response.getresponsestream())             using (irandomaccessstream stream = await path.openasync(fileaccessmode.readwrite))             using (datawriter datawriter = new datawriter(stream))             {                 await task.run(() =>                 {                     int b;                     while ((b = webstream.readbyte()) != -1)                     {                         datawriter.writebyte((byte)b);                         writedbytes++;                         if (writedbytes % (totalbytes / 100) == 0)                             onprogresschanged(new progresseventargs(writedbytes / (totalbytes / 100)));                     }                 });                 await datawriter.storeasync();                 ondownloadcomplete(new eventargs());             }         } } 

progresseventargs code:

public class progresseventargs : eventargs {     public progresseventargs(double percentage)     {         percentage = percentage;     }     public double percentage { get; set; } } 

this working. think it's should faster. sequential bytes reading slow. how can make faster. i'm beginner. please help.

reading , writing large amount of data byte byte may slow down, have millions of method calls downloading 1mb file. should use buffer instead read data in chunks:

... long totalbytesread = 0;  // allocate 4kb buffer each read/write     byte[] buffer = new byte[4 * 1024]; int bytesread;  // read 4kb of data, check if data read while ((bytesread = webstream.read(buffer, 0, buffer.length)) > 0) {    // write 4kb (or less) buffer    datawriter.writebuffer(buffer.asbuffer(0, bytesread));    totalbytesread += bytesread;     // todo: report progresss }     .... 

the optimal buffer size depends on many things, 4kb buffer should fine. here can more info.