SettingsHelpers.cs

using System;
using System.IO;

namespace EnergyScanApi
{
    public static class SettingsHelpers
    {
        public static void AddOrUpdateAppSetting<T>(string sectionPathKey, T value)
        {
            try
            {
                string filePath = Path.Combine(AppContext.BaseDirectory, "appsettings.json");
                string json = File.ReadAllText(filePath);
                dynamic jsonObj = Newtonsoft.Json.JsonConvert.DeserializeObject(json);

                SetValueRecursively(sectionPathKey, jsonObj, value);

                string output = Newtonsoft.Json.JsonConvert.SerializeObject(jsonObj, Newtonsoft.Json.Formatting.Indented);
                File.WriteAllText(filePath, output);

            } catch (Exception ex)
            {
                Console.WriteLine("Error writing app settings | {0}", ex.Message);
            }
        }

        private static void SetValueRecursively<T>(string sectionPathKey, dynamic jsonObj, T value)
        {
            // split the string at the first ':' character
            string[] remainingSections = sectionPathKey.Split(":", 2);

            string currentSection = remainingSections[0];
            if (remainingSections.Length > 1)
            {
                // continue with the procress, moving down the tree
                string nextSection = remainingSections[1];
                SetValueRecursively(nextSection, jsonObj[currentSection], value);
            } else
            {
                // we've got to the end of the tree, set the value
                jsonObj[currentSection] = value;
            }
        }
    }
}