How to hardcode and read a string array in appSettings.json?

Question

I use VSCode and NetCore 1.1.1.

I need to store several datapaths in my appsetting.json to let my console application know where to look for its data.

This is an extract of the appsettings.json file:

{

    "ConnectionStrings":

    {

        "Database": "Filename=./Data/Database/securities_master.db"
    },

    "Data":

    {

     "Folders": ["E:/Data/Folder1/","E:/Data/Folder2/"]

    }
}

I load the configuration file and I want the "Folders" array stored in a variable:

const string APP_SETTINGS_SECTION = "Data";
const string APP_SETTINGS_KEY = "Folders";

var builder = new ConfigurationBuilder().AddJsonFile("appsettings.json", optional: false, reloadOnChange: true);
var configuration = builder.Build();
var dataFolders = configuration.GetSection(APP_SETTINGS_SECTION)[APP_SETTINGS_KEY];

dataFolders is NULL!

If I change my appsetting.json to point only to a single directory like this, everything works:

{

    "ConnectionStrings":

    {

        "Database": "Filename=./Data/Database/securities_master.db"
    },

    "Data":

    {

     "Folders": "E:/Data/Folder1/"   
    }
}

dataFolder = "E:/Data/Folder1/"

So the problem appears to be it doesn't like the string array but to me it looks like a valid Json string array. How should I modify my appsettings (or my C# code) to fix this?

THTP · Accepted Answer · 2017-06-08 10:42:51Z

105

Indexer of a section returns string by exact key match, and since array values have keys with postfixes, there is nothing to match given key and you are getting null.

To get it work you may use something like this

var section = configuration.GetSection($"{APP_SETTINGS_SECTION}:{APP_SETTINGS_KEY}");
var folders = section.Get<string[]>();

And check this for more options.

edited Jun 8, 2017 at 10:42

answered Mar 17, 2017 at 13:29

THTP

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6 Comments

nico9T Over a year ago

var folder = configuration.GetSection(APP_SETTINGS_SECTION)[APP_SETTINGS_KEY]; and var folder2 = configuration.GetSection($"{APP_SETTINGS_SECTION}:{APP_SETTINGS_KEY}").Value; give you the same result: null If there is a string array stored in appsettings.json, a string if there is just a string

THTP Over a year ago

@NicolaPrada, yep, that's true. That's why you should not use Value in this particular case, but parse array with Get<string[]>() extension method.

Brad Over a year ago

This should be the accepted answer. It solves the problem as stated by the OP. Solved my problem, too.

Giova Over a year ago

i agree, this is the best answer, simple and effective

Papa Stahl Over a year ago

Great answer! Just an FYI: This pattern also works with List<string> if you want to return that instead of a string[]: section.Get<List<string>>()

|

2 revs · Accepted Answer · 2017-08-07 15:28:16Z

47

Original answer from here: https://stackoverflow.com/a/42169474/7263255

Works like this:

var someArray = configuration
   .GetSection("SomeArray")
   .GetChildren()
   .Select(x => x.Value)
   .ToArray();

edited Aug 7, 2017 at 15:28

community wiki

2 revs
Halloween_Udo

1 Comment

Mark Dibeh Over a year ago

i like this way . it is easier and more comprehensible

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