ASP.NET MVC FileStreamResult not working as intended

asp.net-mvc stream filestreamresult
pupeno picture pupeno · Jul 13, 2009 · Viewed 11.6k times · Source

I have the following code which I stripped out of any non-essential lines to leave the minimun reproducable case. What I expect is for it to return the image, but it doesn't. As far as I can see it returns an empty file:

public ActionResult Thumbnail(int id) {
    var question = GetQuestion(db, id);
    var image = new Bitmap(question.ImageFullPath);
    MemoryStream stream = new MemoryStream();
    image.Save(stream, ImageFormat.Jpeg);
    return new FileStreamResult(stream, "image/jpeg");
}

Can you identify what's wrong with this code? In the debugger I can see that the stream grows in size so it seems to be getting the data although I haven't been able to verify it's the correct data. I have no idea how to debug the FileStreamResult itself.

Answer

Martin Liversage picture Martin Liversage · Jul 13, 2009

You need to insert

stream.Seek(0, SeekOrigin.Begin);

after the call to

Image.Save()

This will rewind the stream to the beginning of the saved image. Otherwise the stream will be positioned at the end of the stream and nothing is sent to the receiver.

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