Simple AppConfig class that supports caching of the data from the app.config or web.config

Config.cs

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Collections.Concurrent;

namespace Config
{
   public static class AppConfig
    {
        private static readonly AppConfigValues _config = new AppConfigValues();

        public static string MyAppConfigStringValue
            => _config.GetValue<string>("AppConfigStringKey");

        public static int MyAppConfigIntValue
            => _config.GetValue<int>("AppConfigIntKey", 777);
         
        public static string GetTrimmedStringValue
            => _config.GetValue<string>("AppConfigStringKeyTrimmedValue",string.Empty, t => t.TrimEnd('/'));


        private class AppConfigValues
        {
            readonly ConcurrentDictionary<string, dynamic> _configValues = new ConcurrentDictionary<string, dynamic>();
            
            public T GetValue<T>(string field, T defaultValue = default, params Func<T,T>[] additionalExecutionOptions)
            {
                if (_configValues.ContainsKey(field))
                {
                    _configValues.TryGetValue(field, out var val);
                    return val;
                }
                var fieldValue = ConfigurationManager.AppSettings[field];
                T value;
                if (string.IsNullOrWhiteSpace(fieldValue))
                    value = defaultValue;
                else
                    value = (T)Convert.ChangeType(ConfigurationManager.AppSettings[field], typeof(T));

                foreach (var item in additionalExecutionOptions)
                {
                    value = item(value);
                }

                _configValues.TryAdd(field, value);
                return value;
            }
            public T2 GetConvertedValue<T, T2>(string field, Func<T, T2> convertMethod = null, T2 defaultValue = default)
            {
                var convertedKey = $"{field}{typeof(T2)}";
                if (_configValues.ContainsKey(convertedKey))
                {
                    _configValues.TryGetValue(field, out var val);
                    return val;
                }
                var fieldValue = ConfigurationManager.AppSettings[field];
                T2 value;
                if (string.IsNullOrEmpty(fieldValue))
                    value = defaultValue;
                else
                {
                    var originalValue = (T)Convert.ChangeType(ConfigurationManager.AppSettings[field], typeof(T));
                    value = convertMethod(originalValue);
                }
                _configValues.TryAdd(convertedKey, value);
                return value;
            }
        }
    }
}

Approved.

Joey Green Completed the Pull Request