function postSuccess(req,res,next,userId){
    return ms.call('ms.ip.claims.getClaims').then(function(claims){
      return samlp.auth({
        cert: fs.readFileSync('c:\temp\test.pem').toString(),
        key: fs.readFileSync('c:\temp\test.key').toString(),
        signatureAlgorithm: 'rsa-sha1',
        digestAlgorithm:'sha1',
        getPostURL: function(wtrealm,wreply,req,callback){
          callback(null,req.samlRequest.AssertionConsumerServiceURL);
        },
        profileMapper: profileMapper,
        issuer: '<my-company>'
      })(req,res,next);
    });
}

public bool IsValid(XmlDocument xmlDoc)
            {
                var cert = new X509Certificate2();
                cert.Import("c:\temp\test.pfx", "password", X509KeyStorageFlags.DefaultKeySet);
                var manager = new XmlNamespaceManager(xmlDoc.NameTable);
                manager.AddNamespace("ds", SignedXml.XmlDsigNamespaceUrl);
                var nodeList = xmlDoc.SelectNodes("//ds:Signature", manager);
                var signedXml = new SignedXml(xmlDoc);
                signedXml.SignedInfo.CanonicalizationMethod = SignedXml.XmlDsigExcC14NWithCommentsTransformUrl;
                signedXml.LoadXml((XmlElement)nodeList[0]);
                return signedXml.CheckSignature(cert, true);
            }

signedXml.SignedInfo.CanonicalizationMethod = signedXml.XmlDsigExcC14NWithCommentsTransformUrl;