How do I bind a multi level configuration object using IConfiguration in a .net Core application?

Question

I'm trying to bind to a custom configuration object which should be populated by an appsettings.json file.

My appsettings looks a bit like:

{
  "Logging": {
    "IncludeScopes": true,
    "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
    }
  },
  "Settings": {
    "Foo": {
      "Interval": 30,
      "Count": 10
    }
  }
}

The settings classes look like:

public class Settings
{
  public Foo myFoo {get;set;}
}

public class Foo
{
  public int Interval {get;set;}
  public int Count {get;set;}

  public Foo()
  {}

  // This is used for unit testing. Should be irrelevant to this question, but included here for completeness' sake.
  public Foo(int interval, int count)
  {
    this.Interval = interval;
    this.Count = count;
  }
}

When I try to bind the Configuration to an object the lowest level it works:

Foo myFoo = Configuration.GetSection("Settings:Foo").Get<Foo>();

myFoo correctly has an Interval and a Count with values set to 30 and 10 respectively.

But this doesn't:

Settings mySettings = Configuration.GetSection("Settings").Get<Settings>();

mySettings has a null foo.

Frustratingly, if I use the debugger I can see that the necessary data is being read in from the appsettings.json file. I can step down into Configuration => Non-Public Members => _providers => [0] => Data and see all of the information I need. It just won't bind for a complex object.

Answer 1

Your property must match the property names in "appsettings.json".

You must rename your Settings' myFoo property into Foo, because that's property name in the json file.

Answer 2

You can also use the JsonProperty(Included in Newtonsoft.Json) Annotation to tell the serializer what to do like below.

public class Settings
{
  [JsonProperty("Foo")]
  public Foo myFoo {get;set;}
}