how to set an array value in local.settings.json file in azure functions

Question

When I try to insert an array as one of the Values in local.settings.json file:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "",
    "AzureWebJobsDashboard": "",
    "myArray": [
      {
        "key1": "value1",
        "key2": "value2"
      },
      {
        "key1": "value3",
        "key2": "value4"
      }
    ]
  },
  "ConnectionStrings": {
    "SQLConnectionString": "myConnectionString"
  }
}

I start getting exceptions. Can arrays be used in the local.settings.json file? And if they can, what's the correct format?

Answer 1

You need to use the array indexer format.

E.g.

"myArray:[0]:key1": "value1",
"myArray:[0]:key2": "value2",
"myArray:[1]:key1": "value3",
"myArray:[1]:key2": "value4"

Answer 2

Add the array like string in local.settings.json file:

"myArray": "[
             {
               \"key1\": \"value1\",
               \"key2\": \"value2\"
             },
             {
               \"key1\": \"value3\",
               \"key2\": \"value4\"
             }
            ]"

Then deserialize it in your code as below:

string value = Environment.GetEnvironmentVariable("myArray");

objList = JsonConvert.DeserializeObject<List<object>>(value);

Answer 3

This is now possible!

My local settings file looks like this:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true"
  },
  "CustomArray": [
    {
      "CustomProp1": "foo0",
      "CustomProp2": "bar0"
    },
    {
      "CustomProp1": "foo1",
      "CustomProp2": "bar1"
    }
  ]
}

My config when deployed to Azure looks like this:

Then, to resolve the array in my Startup, I have something like this:

var settings = new List<CustomSetting>();
config.GetSection("CustomArray").Bind(settings);

... where CustomSetting is a class like this:

public class CustomSetting 
{
    public string CustomProp1 { get; set; }
    public string CustomProp2 { get; set; }
}

I am using version 3.1.5 of the Microsoft.Extensions.Configuration Nuget package, and version 3.0.7 of the Microsoft.NET.Sdk.Functions Azure Functions SDK.

Answer 4

Can arrays be used in the local.settings.json file? And if they can, what's the correct format?

It seems that arrarys is not supported currently in the local.settings.json.

As far as I know Values collection is expected to be a Dictionary, if it contains any non-string values, it will cause Azure function can not read values from local.settings.json

Based on my test, if it contains it will return null value

 "myArray": [
      {
        "key1": "value1",
        "key2": "value2"
      },
      {
        "key1": "value3",
        "key2": "value4"
      }
    ]