C# ConfigurationManager example

Program.cs

using System;
using System.Configuration;

namespace RuyutConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("WriteSettings");
            WriteSettings("k1", "t1");

            Console.WriteLine("ReadSettings");
            ReadSettings("k1");

            Console.WriteLine("ReadAllSettings:");
            ReadAllSettings();
        }

        private static void WriteSettings(string key, string value)
        {
            try
            {
                var configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
                var settings = configuration.AppSettings.Settings;
                if (settings[key] == null)
                {
                    settings.Add(key, value);
                }
                else
                {
                    settings[key].Value = value;
                }

                configuration.Save(ConfigurationSaveMode.Minimal);
                ConfigurationManager.RefreshSection(configuration.AppSettings.SectionInformation.Name);
            }
            catch (Exception e)
            {
                Console.WriteLine("WriteSettings " + e);
            }
        }

        private static void ReadSettings(string key)
        {
            try
            {
                var appSettings = ConfigurationManager.AppSettings;
                string result = appSettings[key] ?? "Not found";
                Console.WriteLine(result);
            }
            catch (Exception e)
            {
                Console.WriteLine("ReadSettings " + e);
            }
        }

        private static void ReadAllSettings()
        {
            try
            {
                var appSettings = ConfigurationManager.AppSettings;
                if (appSettings.Count == 0)
                {
                    Console.WriteLine("AppSettings is empty.");
                }
                else
                {
                    foreach (var key in appSettings.AllKeys)
                    {
                        Console.WriteLine("key: {0}, Value: {1}", key, appSettings[key]);
                    }
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
            }
        }
    }
}