ASP.NET MVC: FileStreamResult returning too many bytes?

Question

I'm making a call to an MVC controller method. The return type is FileStreamResult. In this method I'm creating an image in the form of a byte array. I'm creating a MemoryStream, passing the byte array in the constructor. I'm then returning a new FileStreamResult object with the memory stream object and "image/png" in the constructor, as my image is a PNG.

public FileStreamResult GetImage()
    {
        ImageModel im = new ImageModel();
        var image = im.GetImageInByteArray();
        var stream = new MemoryStream(image);
        return new FileStreamResult(stream, "image/png");
    }

Now, when I get the request stream from this call, I'm simply using the following method to convert the stream string into a byte array to view the image. However, after this is all done, I end up with 100+ more positions in my byte array than when I return from the MVC controller method call.

public static byte[] ConvertStringToBytes(string input)
    {
           MemoryStream stream = new MemoryStream();

           using (StreamWriter writer = new StreamWriter(stream))
           {
             writer.Write(input);
             writer.Flush();
           }

         return stream.ToArray();
   }

For example, after the "GetImageInByteArray()" call, I have "byte[256]". But when it returns from that MVC call and I convert the response string by putting it through the second method, I end up with "byte[398]";

EDIT QUESTION Is there some kind of divide between the web request I'm making to the GetImage() controller method and what I assume I'm receiving?

I assume what I'm receiving from that call is the memory stream of the image byte array. This is why I'm simply converting that back to a byte array.

Is my assumption here wrong?

Your question is not clear. What are you doing? What is this ConvertStringToBytes method supposed to do? Where/why/how are you calling it in your controller? Why does it take a string parameter and return an array of bytes? Can't you simply use Encoding.UTF8.GetBytes(input)? Why is your image stored as a string? Details please. — Darin Dimitrov
– Darin Dimitrov, Commented Mar 11, 2011 at 20:13
I'm making a call from a class library on the client side to an ASP.NET MVC website's controller method (GetImage()) This is returning a FileStreamResult. That FileStreamResult holds the byte array memory stream which stores my image data. I'm attemting to get that byte array from the response of the MVC controller method call. I'm then converting that array to a base 64 string, then setting it as the source of an image tag in my ASPX view. — ghost_mv
– ghost_mv, Commented Mar 11, 2011 at 20:36

Omar · Accepted Answer · 2011-03-11 21:04:27Z

2

When an MVC action returns a result, it goes through the ASP.NET pipeline which tacks on HTTP headers so that the requestor (browser) can understand what to do with the response.

For an image, these headers might include:

Response Code
Content-Length
Content-Type

Or any other number of custom or typical HTTP headers (Some more HTTP Headers).

If I understand your question correctly, you're converting the entire response from your action to bytes, so naturally, you'll also be converting the headers and anything else the request might return (cookies?).

What are you trying to accomplish with deserialization of the request? Are you trying to test something?

answered Mar 11, 2011 at 21:04

Omar

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1 Comment

ghost_mv Over a year ago

There we go! Thanks Omar, that's what I was suspecting. That the "pipeline" was tacking on additional data. It was my naive assumption that the stream being returned would be all I would be getting back. I'm simply using a third party image generator (barcode) in the middle tier of my application and returning this image to the client to render on the ASPX page. That being said, instead of attempting to utilize the FileStreamResult object, I'm simply using a data transfer object to hold the byte array.

Dawid Kowalski · Accepted Answer · 2011-03-11 20:15:01Z

0

How is your string encoded ? In my opinion it is a problem with encoding.

Try this as your method code:

return (new System.Text.UTF8Encoding()).GetBytes(input);

Greetings

answered Mar 11, 2011 at 20:15

Dawid Kowalski

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2 Comments

ghost_mv Over a year ago

I gave that a shot. Started with byte[270] on the image creation method, then when I ran my request string that I got back from the MVC "GetImage()" controller method through your method I ended up with byte[419].

Dawid Kowalski Over a year ago

hm, you really got me thinking why this is not working, anyway good that you found other solution

ghost_mv · Accepted Answer · 2011-03-11 20:56:58Z

0

I really appreciate your help Dawid, but I decided to simply go another way. I created a transfer object to simply hold the byte array as a property. I serialize this, then pass the object across, deserialize on the opposite end and I have my byte array as it was.

I still am confused on what the HTTP request was tacking onto the memory stream that was being passed, but I just went another route.

answered Mar 11, 2011 at 20:56

ghost_mv

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