How to properly read nested configuration values from config.json in ASP.NET5?

Question

I was following some examples for ASP.NET 5 and I got stumbled with how to properly read "nested" configuration values (if that is the proper term).

Here is relevant portion of config.json:

{
    "ApplicationName" : "OwNextApp",
    "AppSettings": {
        "SiteTitle": "OwNext"
    },
}

And relevant portion of HomeController.cs:

public IActionResult About()
{
    var appNestedNameFailed = _config.Get("AppSettings.SiteTitle");
    var appNestedNameSuccess = _config.Get("AppSettings:SiteTitle");
    var appName = _config.Get("ApplicationName");
    ViewBag.Message = string.Format(@"Your 
        APP NAME: {0};
        APP NESTED NAME FAILED: {1}; 
        APP NESTED NAME SUCCESS: {2}", 
            appName, appNestedNameFailed, appNestedNameSuccess);

    return View();
}

Value for appNestedNameFailed is empty (my initial try before research). And appNestedNameSuccess has value; after I did research and found in tests for Configuration (relevant code shown):

// Assert
Assert.Equal("IniValue1", config.Get("IniKey1"));
Assert.Equal("IniValue2", config.Get("IniKey2:IniKey3"));

Can someone explain why is this the case? Why would it make sense to use : over .? From my interaction with JSON data usually . notation works fine, e.g. How to access nested json data.

Also, I found similar SO question but this does not give explanation of why : was chosen.

Answer 1

That's the convention that we decided upon when we first created the configuration model. We started with json in mind and : is the delimiter there.

Anyways, if you don't want to worry about those conventions, I recommend using the ConfigurationBinder which binds a configuration to a model (a strong type object). Here are the tests on GitHub that can serve as example.