NewTask.cs

using System;
using RabbitMQ.Client;
using System.Text;

class NewTask
{
    public static void Main(string[] args)
    {
        var factory = new ConnectionFactory() { HostName = "localhost" };
        using (var connection = factory.CreateConnection())
        {
            using (var channel = connection.CreateModel())
            {
                channel.QueueDeclare("task_queue", true, false, false, null);

                var message = GetMessage(args);
                var body = Encoding.UTF8.GetBytes(message);

                var properties = channel.CreateBasicProperties();
                properties.SetPersistent(true);

                channel.BasicPublish("", "task_queue", properties, body);
                Console.WriteLine(" [x] Sent {0}", message);
            }
        }
    }

    private static string GetMessage(string[] args)
    {
      return ((args.Length > 0) ? string.Join(" ", args) : "Hello World!");
    }
}