# Azure Functions (in-process) for Service Bus Upgrade Version 5 to 6


## Default topology has changed

This version of the functions integration with Azure Service Bus uses NServiceBus.Transport.AzureServiceBus version 5 and higher. By default Azure Service Bus is configured to the [default topology](/transports/azure-service-bus/topology.md) (using topic-per-event approach). The defaults can be overridden by adding topology options to the Application configuration

The functions integration looks for either topology options placed into `AzureServiceBus:TopologyOptions` or `AzureServiceBus:MigrationTopologyOptions` for migration and backward compatibility scenarios.

<!-- snippet: asb-function-topology-options -->

```cs
class Startup : FunctionsStartup
{
    public override void Configure(IFunctionsHostBuilder builder)
    {
        builder.UseNServiceBus();
    }

    public override void ConfigureAppConfiguration(IFunctionsConfigurationBuilder builder)
    {
        builder.ConfigurationBuilder.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true);
    }
}
```

<!-- endsnippet -->

Using the default topology

<!-- snippet: asb-function-topology-options-json -->

```json
{
  "AzureServiceBus": {
    "TopologyOptions": {
      "PublishedEventToTopicsMap": {
        "MyNamespace.SomeEvent": "some-event"
      },
      "SubscribedEventToTopicsMap": {
        "MyNamespace.SomeEvent": [
          "some-event",
          "some-other-event"
        ]
      },
      "QueueNameToSubscriptionNameMap": {
        "Publisher": "PublisherSubscriptionName"
      }
    }
  }
}
```

<!-- endsnippet -->

Using the migration topology

<!-- snippet: asb-function-topology-migration-options-json -->

```json
{
  "AzureServiceBus": {
    "MigrationTopologyOptions": {
      "TopicToPublishTo": "TopicToPublishTo",
      "TopicToSubscribeOn": "TopicToSubscribeOn",
      "EventsToMigrateMap": [
        "MyNamespace.NotYetMigratedEvent"
      ],
      "SubscribedEventToRuleNameMap": {
        "MyNamespace.NotYetMigratedEvent": "EventRuleName"
      },
      "PublishedEventToTopicsMap": {
        "MyNamespace.MigratedEvent": "MigratedEvent"
      },
      "SubscribedEventToTopicsMap": {
        "MyNamespace.MigratedEvent": "MigratedEvent"
      },
      "QueueNameToSubscriptionNameMap": {
        "Publisher": "PublisherSubscriptionName"
      }
    }
  }
}
```

<!-- endsnippet -->