How to produce Kafka Messages with a Key/Value

The code Asynchronously sends a single message to a Kafka topic.

var producerConfig = new ProducerConfig
{
    Acks = Acks.All,
    BootstrapServers = "localhost:9092"
};
var topic = args.Length > 0 ? args[0] : "test";
var builder = new ProducerBuilder<String, String>(producerConfig);
using (var producer = builder.Build()) //Build a new IProducer implementation Instance
{
      string s = Console.ReadLine();
      while (!s.Contains("exit", StringComparison.InvariantCultureIgnoreCase))
      {
           string[] r = s.Split(":");
           producer.Produce(topic, new Message<string, string> { 
                 Key = r[0],
                 Value = r[1]
                }, (d) =>
                {
                  if (d.Status == PersistenceStatus.Persisted)
                  {Console.WriteLine("Message sent !");}
                 });
                    s = Console.ReadLine();
        }
}