How to convert .OutputStream to byte[] array

Question

Hi Guy I am having dificulty trying to convert from HttpContext.Current.Response.OutputStream to a byte[] array

 

This is my code

byte[] myBuff = new byte[16384];
using (var memoryStream = new System.IO.MemoryStream())
{
HttpContext.Current.Response.OutputStream.CopyTo(memoryStream);
myBuff = memoryStream.ToArray();
}

but I get the following error message "Stream does not support reading." 

the  HttpContext.Current.Response.OutputStream carries an image contentype="image/GIF"

 

Any Idea what I'm missing or doing wrong?

 

TIA