How to extract a list from appsettings.json in .net core

Question

I have an appsettings.json file which looks like this:

{
    \"someSetting\": {
        \"subSettings\": [
            \"one\",
            \"two\",
                 


        

Answer 1

In .NetCore this is what I did:

Normal Setup:

In your appsettings.json create a configuration section for your custom definitions:

    "IDP": [
    {
      "Server": "asdfsd",
      "Authority": "asdfasd",
      "Audience": "asdfadf"
    },
    {
      "Server": "aaaaaa",
      "Authority": "aaaaaa",
      "Audience": "aaaa"
    }
  ]

Create a class to model the objects:

public class IDP
{
    public String Server { get; set; }
    public String Authority { get; set; }
    public String Audience { get; set; }

}

in your Startup -> ConfigureServices

services.Configure<List<IDP>>(Configuration.GetSection("IDP"));

Note: if you need to immediately access your list within your ConfigureServices method you can use...

var subSettings = Configuration.GetSection("IDP").Get<List<IDP>>();

Then in your controller something like this:

Public class AccountController: Controller
{
    private readonly IOptions<List<IDP>> _IDPs;
    public AccountController(IOptions<List<Defined>> IDPs)
    {
        _IDPs = IDPs;
    }
  ...
}

just as an example I used it elsewhere in the above controller like this:

       _IDPs.Value.ForEach(x => {
            // do something with x
        });

Edge Case

In the case that you need multiple configs but they can't be in an array and you have no idea how many sub-settings you will have at any one time. Use the following method.

appsettings.json

"IDP": {
    "0": {
      "Description": "idp01_test",
      "IDPServer": "https://intapi.somedomain.com/testing/idp01/v1.0",
      "IDPClient": "someapi",
      "Format": "IDP"
    },
    "1": {
      "Description": "idpb2c_test",
      "IDPServer": "https://intapi.somedomain.com/testing/idpb2c",
      "IDPClient": "api1",
      "Format": "IDP"
    },
    "2": {
      "Description": "MyApp",
      "Instance": "https://sts.windows.net/",
      "ClientId": "https://somedomain.com/12345678-5191-1111-bcdf-782d958de2b3",
      "Domain": "somedomain.com",
      "TenantId": "87654321-a10f-499f-9b5f-6de6ef439787",
      "Format": "AzureAD"
    }
  }

Model

public class IDP
{
    public String Description { get; set; }
    public String IDPServer { get; set; }
    public String IDPClient { get; set; }
    public String Format { get; set; }
    public String Instance { get; set; }
    public String ClientId { get; set; }
    public String Domain { get; set; }
    public String TenantId { get; set; }
}

Create Extension for Expando Object

public static class ExpandObjectExtension
    {
        public static TObject ToObject<TObject>(this IDictionary<string, object> someSource, BindingFlags bindingFlags = BindingFlags.Instance | BindingFlags.Public)
               where TObject : class, new()
        {
            Contract.Requires(someSource != null);
            TObject targetObject = new TObject();
            Type targetObjectType = typeof(TObject);

            // Go through all bound target object type properties...
            foreach (PropertyInfo property in
                        targetObjectType.GetProperties(bindingFlags))
            {
                // ...and check that both the target type property name and its type matches
                // its counterpart in the ExpandoObject
                if (someSource.ContainsKey(property.Name)
                    && property.PropertyType == someSource[property.Name].GetType())
                {
                    property.SetValue(targetObject, someSource[property.Name]);
                }
            }

            return targetObject;
        }
    }

ConfigureServices

var subSettings = Configuration.GetSection("IDP").Get<List<ExpandoObject>>();

var idx = 0;
foreach (var pair in subSettings)
{

    IDP scheme = ((ExpandoObject)pair).ToObject<IDP>();
    if (scheme.Format == "AzureAD")
    {
        // this is why I couldn't use an array, AddProtecedWebApi requires a path to a config section
        var section = $"IDP:{idx.ToString()}";
        services.AddProtectedWebApi(Configuration, section, scheme.Description);
        // ... do more stuff
        
    }
    idx++;
}

Answer 2

Assuming your appsettings.json looks like this:

{
  "foo": {
    "bar": [
      "1",
      "2",
      "3"
    ]
  }
}

You can extract the list items like so:

Configuration.GetSection("foo:bar").Get<List<string>>()

Answer 3

var settingsSection = config.GetSection["someSettings:subSettings"];
var subSettings = new List<string>;

foreach (var section in settingsSection.GetChildren())
{
    subSettings.Add(section.Value);
}

This should give you the values you need, stored in subSettings

Apologies for bringing up a semi-old thread. I had difficulty finding an answer as a good amount of methods are deprecated, like Get and GetValue. This should be fine if you only need a simple solution without the configuration binder. :)

Answer 4

You can use the Configuration binder to get a strong type representation of the configuration sources.

This is an example from a test that I wrote before, hope it helps:

    [Fact]
    public void BindList()
    {
        var input = new Dictionary<string, string>
        {
            {"StringList:0", "val0"},
            {"StringList:1", "val1"},
            {"StringList:2", "val2"},
            {"StringList:x", "valx"}
        };

        var configurationBuilder = new ConfigurationBuilder();
        configurationBuilder.AddInMemoryCollection(input);
        var config = configurationBuilder.Build();

        var list = new List<string>();
        config.GetSection("StringList").Bind(list);

        Assert.Equal(4, list.Count);

        Assert.Equal("val0", list[0]);
        Assert.Equal("val1", list[1]);
        Assert.Equal("val2", list[2]);
        Assert.Equal("valx", list[3]);
    }

The important part is the call to Bind.

The test and more examples are on GitHub

Answer 5

In my case configuration

 services.Configure<List<ApiKey>>(Configuration.GetSection("ApiKeysList"));

wasn't loaded because the properties were read-only and there were no default constructor

 **//not working** 
  public class ApiKey : IApiKey
    {
        public ApiKey(string key, string owner)
        {
            Key = key;
            OwnerName = owner;
        }
        public string Key { get;  }
        public string OwnerName { get;}
    } 

//Working

    public class ApiKey : IApiKey
    {
        public ApiKey(){}//Added default constructor
        public ApiKey(string key, string owner)
        {
            Key = key;
            OwnerName = owner;
        }
        public string Key { get; set; }        //Added set property
        public string OwnerName { get; set; }  //Added set property
    }