InvalidOperationException: Response Content-Length mismatch when streaming a bitmap

[pathcore-tasos]

Hi there,

If one tries to return an image in a FileStreamResult, the application will throw an exception along the lines of:
InvalidOperationException: Response Content-Length mismatch: too few bytes written (0 of 1234567)

My code was as follows:

private static IActionResult ImageResult(Bitmap image, ImageFormat format, string mimeType)
{
    var stream = new MemoryStream();
    image.Save(stream, format);
    return new FileStreamResult(stream, mimeType);
}

However, if I changed it to the following, the image is returned without complaint:

private static IActionResult ImageResult(Bitmap image, ImageFormat format, string mimeType)
{
    var stream = new MemoryStream();
    image.Save(stream, format);
    return new FileContentResult(stream.ToArray(), mimeType);
}

It appears that doing the reading manually fixes the issue.

Thanks!

[Tratcher]

Did you forget to Seek the stream back to the beginning?

[pathcore-tasos]

Yep that would do it!

Sorry to take up your time!

[HWouters]

I get the same exception one out of two requests. It only happens when I deploy my application to Azure app service. Unfortunately, I can't reproduce it locally.

public class HomeController : Controller
{
    public IActionResult Spa()
    {
        return File("~/index.html", "text/html");
    }
}

[Tratcher]

@HWouters that looks like a different issue. See aspnet/Mvc#6875

[HWouters]

@Tratcher thank you for pointing me to the right issue. The workaround solves my problem until the patch is released.