How to sign a message using X509 certificate in WCF

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C#

ASP.NET

WCF

I am trying to consume a web service that requires message signing for authentication. i have Created the Web service request object and populated it with data.
I have also Created a signature token using the X.509 certificate.
The final aim is to apply the token to web service request so that a digital signature is created for the BODY of the request and that signature should get appended to the request object.
below is the code i am using to generate token :

 public SecurityManager(string serviceActor, bool isClient, string clientActor)
        : base(serviceActor, isClient, clientActor)
    {

    }

    public override void SecureMessage(SoapEnvelope envelope, Security security)
    {
        // Get an X.509 certificate for signing the SOAP message.
        X509SecurityToken signatureToken = GetSecurityToken("subjectName");
        if (signatureToken == null)
        {
            throw new SecurityFault("Message Requirements could not be satisfied.");
        }

        // Add the X.509 certificate to the header.
        security.Tokens.Add(signatureToken);

        // Specify that the SOAP message is signed using this X.509
        // certifcate.
        MessageSignature sig = new MessageSignature(signatureToken);
        security.Elements.Add(sig);

        // Get an X.509 certificate for encrypting the SOAP message.
        X509SecurityToken encryptionToken = GetSecurityToken("subjectName");
        if (encryptionToken == null)
        {
            throw new SecurityFault("Message Requirements could not be satisfied.");
        }

        // Specify that the SOAP message is encrypted using 
        // this X.509 certificate.
        EncryptedData enc = new EncryptedData(encryptionToken);
        security.Elements.Add(enc);
    }

    public X509SecurityToken GetSecurityToken(string subjectName)
    {
        X509SecurityToken objX509SecurityToken = null;
        X509Store objX509Store = new X509Store(StoreName.My, StoreLocation.CurrentUser);
        objX509Store.Open(OpenFlags.ReadOnly);
        try
        {
            X509Certificate2Collection objX509Certificate2Collection = objX509Store.Certificates.Find(X509FindType.FindBySubjectName, subjectName, true);

            X509Certificate2 objX509Certificate2;
            if (objX509Certificate2Collection.Count == 1)
            {
                objX509Certificate2 = objX509Certificate2Collection[0];
                objX509SecurityToken = new X509SecurityToken(objX509Certificate2);
            }
            else
            {
                objX509SecurityToken = null;
            }
        }
        catch (Exception ex)
        {
            objX509SecurityToken = null;
        }
        finally
        {
            if (objX509Store != null)
                objX509Store.Close();
        }
        return objX509SecurityToken;
    }
}

below is the code i am using to create web service request:

        ServiceClient objServiceClient = new ServiceClient();
objServiceClient.send();

I want to know how can i apply security token to my web service request.