How to convert filr into arrary of byte and save again it in file.

//Convert file in arrary of byte
String filepath = Server.MapPath(AsyncFileUpload1.FileName);
byte[] FileByteStream = File.ReadAllBytes(filepath)

//Save arrary of byte into file.
public void SaveFileFromBytes(string FileName, byte[] FileByteStream)
        {
            FileStream targetStream = null;

            Stream sourceStream = new MemoryStream(FileByteStream);

            string uploadFolder = @"~\MyDestinationFolder\";

            System.IO.DirectoryInfo dir = new System.IO.DirectoryInfo(Server.MapPath(uploadFolder));
            if (!dir.Exists)
                dir.Create();

            string filename = FileName;

            string filePath = Path.Combine(Server.MapPath(uploadFolder), filename);

            using (targetStream = new FileStream(filePath, FileMode.Create, FileAccess.Write, FileShare.None))
            {

                const int bufferLen = 4096;

                byte[] buffer = new byte[bufferLen];

                int count = 0;

                while ((count = sourceStream.Read(buffer, 0, bufferLen)) > 0)
                {

                    targetStream.Write(buffer, 0, count);

                }

                targetStream.Close();

                sourceStream.Close();

            }
        }