在fileStream.CopyTo（memoryStream）之后，memoryStream为null

Question

So, I have the function, which gets BitmapImage , I need to save it to iso storage and convert to Base64 (for sending to server). However, copying from fileStream to memoryStream is not successful.

public void SetImage(BitmapImage bitmap)
{
    if (isoFiles.FileExists(Settings.FILE_AVATAR_JPG))
        isoFiles.DeleteFile(Settings.FILE_AVATAR_JPG);

    var fileStream = isoFiles.CreateFile(Settings.FILE_AVATAR_JPG);
    var wb = new WriteableBitmap(bitmap);
    wb.SaveJpeg(fileStream, 120, 120, 0, 85); // file is saved 

    var memoryStream = new MemoryStream();
    fileStream.CopyTo(memoryStream);          // here, memoryStream is null
    byte[] result = memoryStream.ToArray();
    fileStream.Close();

    var base64 = Convert.ToBase64String(result);
}

Answer 1

Stream.CopyTo copies from the current position of fileStream which has been changed by SaveJpeg() so you need to reset it;

var memoryStream = new MemoryStream();

fileStream.Position = 0;
fileStream.CopyTo(memoryStream);