title: Npgsql - NOTIFY event and attach a payload
body: <p>Is it possible to receive a payload when using the <code>NOTIFY</code> psql method?</p>
  
  <p>right now Im using</p>
  
  <pre><code>using (var cmd = new NpgsqlCommand("NOTIFY test", conn)) {
          cmd.ExecuteNonQuery();
  }
  </code></pre>
  
  <p>but I would like to attach a message with the <code>NOTIFY</code> event</p>
  
  <p><strong>to clarify</strong></p>
  
  <pre><code>using (var cmd = new NpgsqlCommand("NOTIFY test_channel, test_message", conn)) {
          cmd.ExecuteNonQuery();
  }
  </code></pre>
  
  <p>this throws an error</p>
  
  <pre><code>Exception has occurred: CLR/Npgsql.PostgresException
  An exception of type 'Npgsql.PostgresException' 
  occurred in System.Private.CoreLib.dll 
  but was not handled in user code: 'External component has thrown an exception.'
  </code></pre>