public override object BeforeSendRequest(ref Message request, System.ServiceModel.IClientChannel channel)
{
	var xml = GetMessageXml(request);
	var elements = xml.GetElementsByTagName("Charge");
  if (elements.Count > 0)
  	XadesSignatureHelper.SignElement(elements[0], Certificates.Authority);
	RebuildMessage(ref request, xml);
	return null;
}

    public class XadesSignatureHelper
    {
        public static void SignElement(XmlNode elementToSign, X509Certificate2 certificate)
        {
            if (elementToSign == null)
                throw new ArgumentNullException("elementToSign");
            if (elementToSign.Attributes == null)
                throw new ArgumentOutOfRangeException("elementToSign", "elementToSign.Attributes == null");

            var attr = elementToSign.Attributes["Id"];
            if (attr == null)
                throw new ArgumentOutOfRangeException("elementToSign", "elementToSign не имеет атрибут Id");
            var chargeId = attr.Value;

            //var xadesSignedXml = new XadesSignedXml(envelopedSignatureXmlDocument);

            var tmpDoc = new XmlDocument() { PreserveWhitespace = true };
            tmpDoc.AppendChild(tmpDoc.ImportNode(elementToSign, true));
            var xadesSignedXml = new XadesSignedXml(tmpDoc);
            

            var reference = new Reference
            {
                DigestMethod = "http://www.w3.org/2001/04/xmldsig-more#gostr3411",
                Uri = "#" + chargeId
            };

            reference.AddTransform(new XmlDsigEnvelopedSignatureTransform());
            reference.AddTransform(new XmlDsigExcC14NTransform());

            xadesSignedXml.AddReference(reference);

            //----------------------AddCertificateInfoToSignature

            var key = certificate.PrivateKey;
            if (key == null)
                throw new ApplicationException("PrivateKey == null");
            xadesSignedXml.SigningKey = key;

            var keyInfo = new KeyInfo();
            keyInfo.AddClause(new KeyInfoX509Data((X509Certificate)certificate));
            //keyInfo.AddClause(new RSAKeyValue((RSACryptoServiceProvider)key));
            xadesSignedXml.KeyInfo = keyInfo;

            //----------------------addXadesInfoButton_Click

            xadesSignedXml.Signature.Id = "signatureId";
            var xadesObject = new XadesObject { Id = "XadesObject", QualifyingProperties = { Target = "#signatureId" } };
            AddSignedSignatureProperties(
                xadesObject.QualifyingProperties.SignedProperties.SignedSignatureProperties,
                xadesObject.QualifyingProperties.SignedProperties.SignedDataObjectProperties,
                xadesObject.QualifyingProperties.UnsignedProperties.UnsignedSignatureProperties,
                certificate);

            xadesSignedXml.AddXadesObject(xadesObject);

            //----------------computeSignatureButton_Click

            xadesSignedXml.SignedInfo.SignatureMethod = "http://www.w3.org/2001/04/xmldsig-more#gostr34102001-gostr3411";
            xadesSignedXml.SignedInfo.CanonicalizationMethod = new XmlDsigExcC14NTransform().Algorithm;
            xadesSignedXml.ComputeSignature();
            xadesSignedXml.SignatureValueId = "signatureValueId";

            //----------------------

            #region requestTimeStampButton_Click

            if (xadesSignedXml.SignatureStandard == KnownSignatureStandard.Xades)
            {
                try
                {
                    var httpTSAClient = new HttpTsaClient();
                    httpTSAClient.RequestTsaCertificate = true; // this.tsaCertificateInResponseCheckBox.Checked;
                    var signatureValueElementXpaths = new ArrayList {"ds:SignatureValue"};
                    var elementIdValues = new ArrayList();
                    var signatureValueHash = httpTSAClient.ComputeHashValueOfElementList(xadesSignedXml.GetXml(),
                                                                                            signatureValueElementXpaths,
                                                                                            ref elementIdValues);
                    httpTSAClient.SendTsaWebRequest("http://testca.cryptopro.ru/tsp/tsp.srf", signatureValueHash);
                    var tsaResponsePkiStatus = httpTSAClient.ParseTsaResponse();
                    if (tsaResponsePkiStatus == KnownTsaResponsePkiStatus.Granted)
                    {
                        var signatureTimeStamp = new TimeStamp("SignatureTimeStamp")
                                                     {
                                                         EncapsulatedTimeStamp =
                                                             {
                                                                 Id = "SignatureTimeStampId",
                                                                 PkiData = httpTSAClient.TsaTimeStamp
                                                             }
                                                     };
                        // this.signatureTimeStampIdTextBox.Text;
                        var hashDataInfo = new HashDataInfo {UriAttribute = "#" + elementIdValues[0]};
                        signatureTimeStamp.HashDataInfoCollection.Add(hashDataInfo);
                        var unsignedProperties = xadesSignedXml.UnsignedProperties;
                        unsignedProperties.UnsignedSignatureProperties.SignatureTimeStampCollection.Add(signatureTimeStamp);
                        xadesSignedXml.UnsignedProperties = unsignedProperties;

                        var xml = xadesSignedXml.XadesObject.GetXml();
                        var xml1 = xadesSignedXml.GetXml();

                        elementToSign.AppendChild(elementToSign.OwnerDocument.ImportNode(xadesSignedXml.GetXml(), true));
                    }
                    else
                        throw new ApplicationException("TSA timestamp request not granted: " + tsaResponsePkiStatus.ToString());
                }
                catch (Exception exception)
                {
                    throw new ApplicationException("Exception occurred during TSA timestamp request: " + exception.ToString());
                }
            }
            else
                throw new ApplicationException(
                    "Signature standard should be XAdES. (You need to add XAdES info before computing the signature to be able to inject a timestamp)");

            #endregion requestTimeStampButton_Click

            //-------------------------------------------------
        }

        private static void AddSignedSignatureProperties(SignedSignatureProperties signedSignatureProperties, SignedDataObjectProperties signedDataObjectProperties,
            UnsignedSignatureProperties unsignedSignatureProperties, X509Certificate2 certificate)
        {
            XmlDocument xmlDocument;
            Cert cert;

            //xmlDocument = new XmlDocument();

            cert = new Cert();
            cert.IssuerSerial.X509IssuerName = certificate.IssuerName.Name;
            cert.IssuerSerial.X509SerialNumber = certificate.SerialNumber;
            cert.CertDigest.DigestMethod.Algorithm = SignedXml.XmlDsigSHA1Url;
            cert.CertDigest.DigestValue = certificate.GetCertHash();
            signedSignatureProperties.SigningCertificate.CertCollection.Add(cert);
            signedSignatureProperties.SigningTime = DateTime.Now;
            signedSignatureProperties.SignaturePolicyIdentifier.SignaturePolicyImplied = true;
        }
    }

public const string XadesNamespaceUri = "http://uri.etsi.org/01903/v1.1.1#"; // было "http://uri.etsi.org/01903/v1.3.2#";
public const string SignedPropertiesType = "http://uri.etsi.org/01903/v1.1.1#SignedProperties";  // было "http://uri.etsi.org/01903/v1.3.2#SignedProperties";