example.cs

var parsedEvent = JsonParser.Default.Parse<ParsedDataEventWebhook>(json);

//verify the signature to validate the webhook came from RP
var key = "CIO_SECRET"; //this should be your CIO auth secret
var encoding = BinaryStringEncoding.Utf8;
  var algorithmProvider = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA256");
    var contentBuffer =
CryptographicBuffer.ConvertStringToBinary(parsedEvent.checksum,
encoding);
   var keyBuffer = CryptographicBuffer.ConvertStringToBinary(key, encoding);
   var signatureKey = algorithmProvider.CreateKey(keyBuffer);
   var signedBuffer = CryptographicEngine.Sign(signatureKey, contentBuffer);

   if (CryptographicBuffer.EncodeToHexString(signedBuffer) !=
parsedEvent.signature) {
    //reject signature
    return false;
   }

   //verify the checksum to validate the body wasn't tampered with
var encoding = BinaryStringEncoding.Utf8;
  var algorithmProvider = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA256");
    var webhookIdBuffer =
CryptographicBuffer.ConvertStringToBinary(parsedEvent.webhook_id,
encoding);
   var eventBuffer =
CryptographicBuffer.ConvertStringToBinary(parsedEvent.data_event,
encoding);

   if (CryptographicBuffer.EncodeToHexString(webhookIdBuffer +
eventBuffer) != parsedEvent.checksum) {
    //reject checksum
    return false;
   }

   //now you can process the rest of your webhook data