Azure functions local.settings.json represented in appsettings.json for a ServiceBusTrigger

Question

I currently have an azure function using the ServiceBusTrigger binding

 [ServiceBusTrigger("%TopicName%", "%SubscripionName%", Connection = "MyConnection")]
         string  catclogueEventMsgs, ILogger log, ExecutionContext context)

which uses this local.settings.json file

   "Values": {
             …
    "MyConnection": "Endpoint=sb://testxxxxxxxxxxxxxxxxxx
    "SubscriptionName": "testsubscriptionName"
    "TopicName": "testtopicName",
  }

How do I represent this in the appsettings.json file. Will it be like the below?

   "Values": {
    "MyConnection": "Endpoint=sb://testxxxxxxxxxxxxxxxxxx
    "SubscriptionName": "testsubscriptionName"
    "TopicName": "testtopicName",
  }

Instead of using a “Values” object can I use eg “MySubs” object like the below?

   "MySubs": {
    "MyConnection": "Endpoint=sb://testxxxxxxxxxxxxxxxxxx
    "SubscriptionName": "testsubscriptionName"
    "TopicName": "testtopicName",
  }

If its possible to use the above settings, how do I represent this in the ServiceBusTrigger binding? would i change it to this?

 [ServiceBusTrigger("%MySubs.TopicName%", "%MySubs.SubscripionName%", Connection = "MySubs.MyConnection")]
         string  catclogueEventMsgs, ILogger log, ExecutionContext context)

Solution

You CAN indeed read settings outside the Values array as follows:

WeatherApiConfig.cs

public class WeatherApiConfig
{
    public string WeatherApiUrl { get; set; }
    public string WeatherApiKey { get; set; }
}

New for Azure Functions V2, we have an appropriate way to handle DI as shown below:

Startup.cs

[assembly: FunctionsStartup(typeof(BlazingDemo.Api.Startup))]

namespace BlazingDemo.Api
{
    public class Startup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            var config = new ConfigurationBuilder()
                .SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("local.settings.json", optional: true, reloadOnChange: true)
                .AddEnvironmentVariables()
                .Build();

            var apiConfig = new WeatherApiConfig();
            config.Bind(nameof(WeatherApiConfig), apiConfig);

            builder.Services.AddSingleton(apiConfig);
            builder.Services.AddHttpClient();
        }
    }
}

Local.settings.json

{  
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet"
  },
  "WeatherApiConfig": {
    "WeatherApiUrl": "http://api.openweathermap.org/data/2.5/weather",
    "WeatherApiKey": "**removed**"
  }
}

Note: The key for me was to add .SetBasePath(Directory.GetCurrentDirectory()) in Startup.cs since it couldn't find the file without it.

In production I use the function app's Application Settings section to configure these two properties as follows:

Comments

[Adam Tuliper]

This is a neat workaround. I just want to call out this uses then a new instance of the configuration system and your dependency injection is no longer IOptions<T> based. If you want that or want that in addition to this you'll still need to configure that via builder.Services.AddOptions<>().Configure<Iconfiguration>() etc at least as of v3.