var deviceId = "2c8540ee-85df-4f1a-b35f-00124e1d3c4a";

var caCert = new X509Certificate2("c:\\certs\\iothub_ca.crt");   // From https://github.com/Azure/azure-iot-sdk-c/blob/master/certs/certs.c
var clientCert = new X509Certificate2("C:\\certs\\device.pfx");

var client = new MqttClient(
    "my-iot-hub.azure-devices.net", 
    MqttSettings.MQTT_BROKER_DEFAULT_SSL_PORT, true,
    caCert,
    clientCert,
    MqttSslProtocols.TLSv1_2);
    
client.Connect(deviceId);

client.Publish($"devices/{deviceId}/messages/events/", Encoding.UTF8.GetBytes("Hello"));