Apply transform to a xml file.

  /// <summary>
        /// Applies the transform to the xml document.
        /// </summary>
        /// <param name="doc">The doc.</param>
        /// <returns></returns>
        private static Stream ApplyTransform(XmlDocument doc)
        {
            XmlDsigEnvelopedSignatureTransform env = new XmlDsigEnvelopedSignatureTransform();
            env.LoadInput(doc.Clone());
            object output1 = env.GetOutput();
            Transform c14n = new XmlDsigExcC14NTransform();//(Transform)CryptoConfig.CreateFromName("http://www.w3.org/TR/2001/REC-xml-c14n-20010315");
            c14n.LoadInput(output1);
            Stream endObject = (Stream)c14n.GetOutput();
            return endObject;
        }