How to map a sub-array in Options into a Dictionary

Question

My options in appsettings.json look like this:

  "ApplicationSettings": {
    "Value1": "abc",
    "Value2": 5,
    ...
    "MaxDOP": [
      {
        "Region": "A",
        "ThreadCount": 20
      },
      {
        "Region": "B",
        "ThreadCount": 30
      },
      ...
    ]
  }

I inject it as usual:

services.Configure<Models.AppConfigModel>(Configuration.GetSection("ApplicationSettings"));

The problem for me is how to map the MaxDOP array so that it will maintain the up-to-date sync via IOptionsMonitor<>. This question deals with arrays in general, but in my case the Region attribute is unique, and I would rather like a Dictionary<string, int> (or possibly Dictionary<string, MaxDopSettings> in case I will ever have more than one non-key value there) so that I could search by the region code efficiently.

Can it be done?

Answer 1

Solution 1: Map a dictionary

Change the signature of MaxDOP from list to dictionary

"MaxDOP": {
    "A": {
      "ThreadCount": 20
    },
    "B": {
      "ThreadCount": 30
    }
}

Dop class:

public class Dop
{
    public int ThreadCount { get; set; }
}

Configuring:

services.Configure<Dictionary<string, Dop>>(Configuration.GetSection("ApplicationSettings:MaxDOP"));

Usage:

public HomeController(IOptionsMonitor<Dictionary<string, Dop>> monitor)
{
    _monitor = monitor;
    Dictionary<string, Dop> a = _monitor.CurrentValue;
}

---

Solution 2: Include dictionary into main settings POCO

Change the signature of MaxDOP from list to dictionary:

appsettings.json:

"ApplicationSettings": {
    "Value1": "abc",
    "Value2": 5,
    "MaxDOP": {
      "A": {
        "ThreadCount": 20
      },
      "B": {
        "ThreadCount": 30
      }
    }
  }

Poco classes:

public class ApplicationSettings
{
    public string Value1 { get; set; }
    public int Value2 { get; set; }
    public Dictionary<string, Dop> MaxDOP { get; set; }
}

public class Dop
{
    public int ThreadCount { get; set; }
}

Configuring:

services.Configure<ApplicationSettings>(Configuration.GetSection("ApplicationSettings"));

Usage:

public HomeController(IOptionsMonitor<ApplicationSettings> monitor)
{
    _monitor = monitor;
    ApplicationSettings a = _monitor.CurrentValue;
}