OutputStream is not available when a custom TextWriter is used

Question

this is my function which converts pdf to png image, it's throwing an error on this line--> stream.WriteTo(Response.OutputStream); Is there some thing wrong??

protected void CreatePngFromPdf() 
        {

            try
            {

                string PDFLocation = string.Format(@"\\XXXX\{0}\{1}\{2}.pdf", Yr, Loc.Substring(0, 4), Loc.Substring(4, 4));
                Utilities.WebPDF.PDF WebPDF = new DocuvaultMVC.Utilities.WebPDF.PDF();

                WebPDF.Credentials = new NetworkCredential(@"xyz", "xyz");
                byte[] png = WebPDF.StreamPdfPageAsPngResize(PDFLocation,PageNumber, 612, 792);

                MemoryStream ms = new MemoryStream(png);
                MemoryStream stream = new MemoryStream();
                int newWidth = 612;
                int newHeight = 792;
                System.Drawing.Image newImg = System.Drawing.Image.FromStream(ms);

                Bitmap temp = new Bitmap(newWidth, newHeight, newImg.PixelFormat);
                Graphics newImage = Graphics.FromImage(temp);
                newImage.DrawImage(newImg, 0, 0, newWidth, newHeight);
                newImg.Dispose();

                temp.Save(stream, ImageFormat.Png);
                stream.WriteTo(Response.OutputStream);
                temp.Dispose();
                stream.Dispose();
            }
            catch (Exception ex)
            {
                Response.Write(ex.Message.ToString());
            }
        }

Answer 1

This is not directly relevant to your problem, but I got the same exception when doing something else, so I thought I'd put that answer here for posterity...

I got this exception merely when the homepage was rendering, rather than when going to the relevant controller action.

Much head-scratching ensues, until I realise that I've used Html.Action (which runs the action and emits the HTML inline) rather than Url.Action (which generates the URL).

Answer 2

In my case the reason was wrong argument in Controller.File method.

Controller.File method with third parameter as null will render the image in the browser window:

public ActionResult GenerateImage(...)
{
    ...
    return File(fileResult.Buffer, fileResult.ContentType, null);
}

Controller.File method with third parameter as filename will trigger downloading of the image in the browser:

public ActionResult GenerateImage(...)
{
    ...
    return File(fileResult.Buffer, fileResult.ContentType, "image.jpg");
}

Controller.File method with third parameter as extension will cause the error: OutputStream is not available when a custom TextWriter is used

public ActionResult GenerateImage(...)
{
    ...
    return File(fileResult.Buffer, fileResult.ContentType, ".jpg");
}