Custom Output Filter for a C# Web Services SDK Client

The following code fragment shows the custom output filter for the custom security assertion. The custom filter provides three methods:

`CustomSecurityClientOutputFilterHok`	Class constructor that creates token and message signature objects for the SOAP message.
`SecureMessage`	An override method for the .NET method SendSecurityFilter.SecureMessage. The override method adds the SAML token and message signature to the .NET Security element.
`CreateKeyInfoSignatureElement`	Creates an XML document that specifies the SAML token type and ID.

Output Filter for the Custom SecurityPolicyAssertion

internal class CustomSecurityClientOutputFilterHok : SendSecurityFilter
{
  IssuedToken issuedToken = null;
  string samlAssertionId = null;
  MessageSignature messageSignature = null;

  /// Create a custom SOAP request filter.
  /// (Save the token and certificate.)
  public CustomSecurityClientOutputFilterHok(CustomSecurityAssertionHok parentAssertion)
         : base(parentAssertion.ServiceActor, true)
  {
    issuedToken = new IssuedToken(parentAssertion.BinaryToken, parentAssertion.TokenType);
    samlAssertionId = parentAssertion.BinaryToken.Attributes.GetNamedItem("ID").Value;
    messageSignature = new MessageSignature(parentAssertion.SecurityToken);
  }

  ///  Secure the SOAP message before its sent to the server.
  public override void SecureMessage(SoapEnvelope envelope, Security security)
  {
    //create KeyInfo XML element
    messageSignature.KeyInfo = new KeyInfo();
    messageSignature.KeyInfo.LoadXml(CreateKeyInfoSignatureElement());

    security.Tokens.Add(issuedToken);
    security.Elements.Add(messageSignature);
  }

  /// Helper method to create a custom key info signature element.
  /// Returns Key info XML element.
  private XmlElement CreateKeyInfoSignatureElement()
  {
    var xmlDocument = new XmlDocument();
    xmlDocument.LoadXml(@"<root><SecurityTokenReference 
    xmlns=""http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"" 
    xmlns:wsse=""http://docs.oasis-open.org/wss/oasis-wss-wssecurity-secext-1.1.xsd"" 
    wsse:TokenType=""http://docs.oasis-open.org/wss/oasis-wss-saml-token-profile-1.1#SAMLV2.0"">
    <KeyIdentifier
    xmlns=""http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"" 
    ValueType=""http://docs.oasis-open.org/wss/oasis-wss-saml-token-profile-1.1#SAMLID"">"
    + samlAssertionId + @"</KeyIdentifier></SecurityTokenReference></root>");
    return xmlDocument.DocumentElement;
  }