.NET - Topic.Subscribe()

Subscribe a handler to a topic and receive new events for processing.

using Nitric.Sdk;

class EventUpdate
{
  public string Message { get; set; }
}

var updates = Nitric.Topic<EventUpdate>("updates");

updates.Subscribe(ctx => {
  Console.WriteLine(ctx.Req.Payload);

  return ctx;
});

Nitric.Run();

Parameters

Name
middleware
Required
Required
Type
Func<EventContext, EventContext> or Middleware<EventContext>[]
Description
The middleware (code) to be triggered by the topic.

Examples

using Nitric.Sdk;

var updates = Nitric.Topic("updates");

updates.Subscribe(ctx => {
  Console.WriteLine(ctx.Req.Payload);

  return ctx;
});

Nitric.Run();

Subscibe to a topic with chained middleware

using Nitric.Sdk;

class EventUpdate
{
  public string Message { get; set; }
}

var updates = Nitric.Topic<EventUpdate>("updates");


updates.Subscribe((ctx, next) =>
  {
    // Validate request
    if (invalidRequest(ctx))
    {
      return ctx;
    }
    return next(ctx);
  }, (ctx, next) => {
    // Handle request
    return next(ctx);
  }
);

Nitric.Run();

Notes

A function may only subscribe to a topic once, if multiple subscribers are required, create them in different functions.
A function may subscribe to OR publish to a topic but not both

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Last updated on May 9, 2025