Dynamic Wrapper for the values in the ConfigurationManager.AppSettings dictionary.

AppSettings.cs

using System.Configuration;
using System.Dynamic;
using System.Linq;

namespace AppSettingsDemo
{
    /// <summary>
    /// Wrapper for the values in the ConfigurationManager.AppSettings dictionary.
    /// Declare an instance of the AppSettings class with the dynamic keyword and all calls
    /// to any properties will lookup for the right key in the appSettings-section in you app.config
    /// </summary>
    public class AppSettings : DynamicObject
    {
        public override bool TryGetMember(GetMemberBinder binder, out object result)
        {
            if (ConfigurationManager.AppSettings.AllKeys.Contains(binder.Name))
            {
                result = ConfigurationManager.AppSettings[binder.Name];
                return true;
            }
            throw new ConfigurationErrorsException(
                $"There is no key \"{binder.Name}\" in appSettings-section in your application config.");
        }
    }
}