Table of Contents

Reading Headers

Kafka and MQTT 5 support custom headers (called user properties in MQTT). In Silverback you can access them either via the inbound envelope or by mapping them to model properties.

Subscribe to IInboundEnvelope<TMessage>

Subscribe to IInboundEnvelope<TMessage> to access the message and its metadata (headers, broker-specific data, etc.). The envelope exposes a Headers collection.

public class MySubscriber
{
    public async Task HandleAsync(IInboundEnvelope<MyMessage> envelope)
    {
        int priority = envelope.Headers.GetValue<int>("x-priority");

        // ...
    }
}

Use HeaderAttribute on the Message Model

Decorate message properties with HeaderAttribute to map header values into the model.

using Silverback.Messaging.Messages;

public class OrderCreatedEvent
{
    [Header("x-order-type")]
    [JsonIgnore]
    public OrderType OrderType { get; set; }

    [Header("x-books-order")]
    public bool ContainsBooks => Items.Any(item => item.Type == "book");
}
Important

Only the message type is scanned. Properties decorated with HeaderAttribute must be declared on the root message object (not nested types).

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