Subscriptions with Request Responses

Subscribing to a request event allows users to respond with a different object. This is useful for RPC-like communication.

• RequestAsync
• SubscribeRequest

Publish Requests with Awaited Responses

using Lite.EventIpc;

public async Task SubscribeWithResponse()
{
  // Subscribe to Ping events that respond with Pong
  _eventAggregator.SubscribeRequest<Ping, Pong>(EventSubscribe_PingAsync);

  // Send a Ping request event and await the Pong response
  Ping ping = new Ping("HELLO!");
  Pong? response = await _eventAggregator.RequestAsync<Ping, Pong>(ping);

  if (response is not null)
  {
    // Received PONG!
  }
}

private async Task<Pong> EventSubscribe_PingAsync(Ping ping)
{
  var response = "Received PING loud and clear";
  return new Pong(response);
}

Handling Request Event Timeouts

Borrowing from the previous example, you can specify a timeout when sending a request event. If no subscriber responds within the timeout period, null is returned.

public async Task SubscribeWithResponse()
{
  // ...

  // Send a Ping request event and await the Pong response
  Ping ping = new Ping("HELLO!");
  var timeout = TimeSpan.FromMilliseconds(3000);

  Pong? response = null;
  try
  {
    response = await _eventAggregator.RequestAsync<Ping, Pong>(ping, timeout);
  }
  catch (TimeoutException)
  {
    // Handle timeout (no response received in time)
  }

  // ...
}