Service Bus Topics

Getting Started

First begin by creating an empty Azure Functions v2 project and then install the core nuget packages for Function Monkey:

Install-Package FunctionMonkey
Install-Package FunctionMonkey.Compiler

You will also need to add the Service Bus trigger bindings:

Install-Package Microsoft.Azure.WebJobs.ServiceBus

In our hyptotheitcal solution we're going to listen to new user registration messages on a topic subscription, begin by Now creating a folder in the solution called commands and create a class called NewUserRegistrationCommand:

public class NewUserRegistrationCommand : ICommand
{
    public Guid UserId { get; set; }

    public string Username { get; set; }

    public string EmailAddress { get; set; }
}

Next create a folder in the solution called Handlers and create a class called NewUserRegistrationCommandHandler:

internal class NewUserRegistrationCommandHandler : ICommandHandler<NewUserRegistrationCommand>
{
    public Task ExecuteAsync(NewUserRegistrationCommand command)
    {
        // We're not really going to do anything here
        return Task.CompletedTask;
    }
}

And now we'll create our function app configuration in the root of the project that registers the command handler and registers the command with a service bus topic and subscription:

public class FunctionAppConfiguration : IFunctionAppConfiguration
{
    private const string TopicName = "newuserregistration";
    private const string SubscriptionName = "telemetrysubscription";
    private const string ServiceBusConnectionName = "serviceBusConnection";

    public void Build(IFunctionHostBuilder builder)
    {
        builder
            .Setup((serviceCollection, commandRegistry) =>
                commandRegistry
                    .Register<NewUserRegistrationCommandHandler>()
            )
            .Functions(functions => functions
                .ServiceBus(ServiceBusConnectionName, serviceBus => serviceBus
                    .SubscriptionFunction<NewUserRegistrationCommand>(TopicName, SubscriptionName)
                )
            );
    }
}

Finally we need to create an entry in local.settings.json for the Service Bus connection string:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "AzureWebJobsDashboard": "UseDevelopmentStorage=true",
    "serviceBusConnection": "<connection string>" 
  }
}

And that's it! If you run this project having created a topic and subscription with the appropriate names and use a real connection string you'll find that the SendEmailCommandHandler is invoked for each item you place on the queue.

Note that it is possible to omit the connection setting name - see default connection settings for more details.

Validation

If you want to validate the queue messages as you recieve them then validation is supported and is documented here.

Sample Code

The source code for the above can be found over in GitHub.