Configure ServiceBusTriggerAttribute from AppSettings

Been in the same boat. It is already done.

Have a look at this sample function here and in the AnalyseImage.cs file at the trigger attribute:

[FunctionName("ReviewImageAndText")]
  public static async Task ReviewImageAndText(
  [QueueTrigger("%queue-name%")]  ReviewRequestItem queueInput,
  [Blob("input-images/{BlobName}", FileAccess.Read)]  Stream image,
  [DocumentDB("customerReviewData", "reviews", Id = "{DocumentId}", PartitionKey = "Reviews", ConnectionStringSetting = "customerReviewDataDocDB")]  dynamic inputDocument)
  {

In the QueueTrigger, the ‘%’ is specifying that it wants to be resolved from a setting. This will look (when deployed on azure) at the WebApp settings you can set via arm. When running functions locally, they are defined in the local.settings.json as you can see in the sample app, that the queue-name has been assigned there.

In the ARM template, as normal, resolve and apply the values as settings in the web app properties with the same name as you use for the config setting in local.settings.json, which is the same as between the %'s

In my case i have config for keyvault loaded first, then I have to load keyvault, then I have to deserialize my credentials from keyvault and only then I can have the service bus connection string to bind to. It took me a bit of time to get it right, but here’s the solution in case someone else runs into same issue. Hope it helps someone!

           // Gets the default configuration so we can load keyvault
            var bootstrapConfig = new ConfigurationBuilder()
                .AddEnvironmentVariables("config:") //this only picks app settings that start with "config:" and at the same time strips off "config;" after load
                .Build();

           //get the keyvault URL from current config
           var keyvault = bootstrapConfig["VaultBaseUrl"];

            // Creates a new config based on the default one and adds the keyvault configuration builder
            var keyVaultConfig = new ConfigurationBuilder()
                .AddConfiguration(bootstrapConfig)
                .AddAzureKeyVault(keyvault)
                .Build();

            //this is my custom step to deserialize JSON in mycustomsecret to an POCO that I can work with
            var credentials = CredentialManager.GetFromString(keyVaultConfig["mycustomsecret"]);

            //this is needed for the servicebus function binding to work properly
            Environment.SetEnvironmentVariable($"dynamic:ServiceBusConnectionString", credentials.ConnectionStrings.ServiceBus);

            //creates a final config including dynamic environment variables used for function bindings like ServiceBus
            var config = new ConfigurationBuilder()
                .AddConfiguration(keyVaultConfig)
                .AddEnvironmentVariables("dynamic:") //this only picks app settings that start with "dynamic:" and at the same time strips off "dynamic;" after load
                .Build();

            //this is required to replace the IConfiguration with current settings otherwise the new Environment variable isn't picked up
            builder.Services.AddSingleton<IConfiguration>(config);

Now when setting up the binding for the function I can reference the new environment variable

        [ServiceBusAccount("ServiceBusConnectionString")]
        [FunctionName("ProcessMessage")]
        public async Task ProcessMessage([ServiceBusTrigger("%myQueueName%")] Message message, ILogger log, CancellationToken cancellationToken, MessageReceiver messageReceiver)
        {
              var request = JsonConvert.DeserializeObject<dynamic>(Encoding.UTF8.GetString(message.Body));
        }

local.settings.json NOTE: You will get a warning on build/run that ServiceBusConnectionString doesn’t exist in local.settings.json

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "config:VaultBaseUrl": "https://MYKEYVAULT.vault.azure.net",
    "myQueueName": "service-bus-dev-queue"
  }
}