How to create byte array from HttpPostedFile

BinaryReader b = new BinaryReader(file.InputStream);
byte[] binData = b.ReadBytes(file.InputStream.Length);

line 2 should be replaced with

byte[] binData = b.ReadBytes(file.ContentLength);

It won't work if your file InputStream.Position is set to the end of the stream. My additional lines:

Stream stream = file.InputStream;
stream.Position = 0;

in your question, both buffer and byteArray seem to be byte[]. So:

ImageElement image = ImageElement.FromBinary(buffer);

Use a BinaryReader object to return a byte array from the stream like:

byte[] fileData = null;
using (var binaryReader = new BinaryReader(Request.Files[0].InputStream))
{
    fileData = binaryReader.ReadBytes(Request.Files[0].ContentLength);
}