Can not deserialize appsettings IConfiguration section into array of typed elements

Question

I am trying to retrieve an IConfiguration section from my appsettings.json file which is an array of strongly typed elements and i keep getting an empty collection. I am using whatever Asp .Net Core 3.1 uses by default when deserializing the IConfiguration section:

(I am using JsonSerializer for all json specific tasks )

DTO

public class Element
{
   [JsonPropertyName("key")]
   public string Key {get;set;}
   [JsonPropertyName("value")]
   public string Value{get;set;}
}

public class Elements
{
   [JsonPropertyName("fields")]
   public IEnumerable<Element>Fields{get;set;}
}
public class Config
{
   [JsonPropertyName("elements")]
   public Elements Elements{get;set;}
}

appsettings.json

{
  "config":{
    "fields":[
      {"key":"a","value":"aa"},
      {"key":"b","value":"bb"},
      {"key":"c","value":"cc"}
   }
}

Startup

public class Startup
    {
        public IConfiguration Configuration { get; }

        public Startup(IConfiguration configuration) {
            this.Configuration = configuration;
        }
        public void ConfigureServices(IServiceCollection services) {
            Config config=this.Configuration.GetSection("config").Get<Config>(); // elements count is 0
            Elements elements =  this.Configuration.GetSection("config:elements").Get<Elements>();  // elements count is 0
            
        }
}

I have tried :

• Changing my IEnumerable of typed elements (Elements) to Array,List,IList to no avail
• Placing my Elements field directly in the root to no avail

P.S
If i change from [SomeCollection]<Element> to [SomeCollection]<string> it sees all the elements , so there is obviously a problem when deserializing collections of types.

Answer 1

You can change Elements to List<Element>,here is a demo:

DTO:

public class Element
    {
        [JsonPropertyName("key")]
        public string Key { get; set; }
        [JsonPropertyName("value")]
        public string Value { get; set; }
    }


    public class Config
    {
        [JsonPropertyName("fields")]
        public List<Element> Fields { get; set; }
    }

Startup:

Config config=this.Configuration.GetSection("config").Get<Config>(); 

Update:

Another way:

DTO:

public class Element
{
   [JsonPropertyName("key")]
   public string Key {get;set;}
   [JsonPropertyName("value")]
   public string Value{get;set;}
}

public class Elements
{
   [JsonPropertyName("fields")]
   public IEnumerable<Element>Fields{get;set;}
}
public class Config
{
   [JsonPropertyName("elements")]
   public Elements Elements{get;set;}
}

Startup:

Elements elements = this.Configuration.GetSection("config").Get<Elements>(); 
Config config= new Config { Elements = elements };