[DotNetDevelopment] Exception : Parameter is not valid

[shree]

hello all,
here I am extracting images from pdf file
I am getting data in bytes[] successfully;
 but when I am trying to cast it in Image Object it throws exception
as
" Parameter is not valid "

here is my code ...

MemoryStream stream = new MemoryStream(bytes);
                                    stream.Position = 0;
                                    Image img =
Image.FromStream(stream,true,false);