AppSettingsHelper.cs

    public static class AppSettingsHelper
    {
        /// <summary>
        /// Get the value or type default
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="name"></param>
        /// <returns></returns>
        public static T GetValue<T>(string name)
        {
            return GetValue(name, default(T));
        }

        /// <summary>
        /// Get the value or default
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="name"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static T GetValue<T>(string name, T defaultValue)
        {
            try
            {
                var converter = TypeDescriptor.GetConverter(typeof(T));
                var value = ConfigurationManager.AppSettings[name];
                if (!string.IsNullOrEmpty(value))
                {
                    return (T)converter.ConvertFromString(value);
                }
            }
            catch (Exception)
            {
                //NotSupportedException: don't care
                //Other: Ignore
            }
            return defaultValue;
        }

        /// <summary>
        /// Get the first key that exists
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="names"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static T GetValue<T>(IEnumerable<string> names, T defaultValue)
        {
            foreach (var name in names)
            {
                if (ConfigurationManager.AppSettings.AllKeys.Contains(name, StringComparer.InvariantCultureIgnoreCase))
                {
                    return GetValue(name, defaultValue);
                }
            }
            return defaultValue;
        }

        /// <summary>
        /// Get folder name and create if it doesn't exist.
        /// </summary>
        /// <param name="name"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static string GetDirectory(string name, string defaultValue)
        {
            var directoryPath = ConfigurationManager.AppSettings[name] ?? defaultValue;
            if (string.IsNullOrEmpty(directoryPath))
                return string.Empty;                        
            try
            {
                if (!Directory.Exists(directoryPath))
                {
                    Directory.CreateDirectory(directoryPath);
                }
            }
            catch (Exception)
            {
                // Ignore the exception here. Wait for a file not exists later.
            }
            return directoryPath;
        }

        /// <summary>
        /// Get file name and create if it doesn't exist.
        /// </summary>
        /// <param name="name"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static string GetFile(string name, string defaultValue)
        {
            var filePath = ConfigurationManager.AppSettings[name] ?? defaultValue;
            if (string.IsNullOrEmpty(filePath))
                return string.Empty;
            try
            {
                var directoryPath = Path.GetDirectoryName(filePath);
                if (!string.IsNullOrEmpty(directoryPath) && !Directory.Exists(directoryPath))
                {
                    Directory.CreateDirectory(directoryPath);
                }
            }
            catch (Exception)
            {
                // Ignore the exception here. Wait for a file not exists later.
            }
            return filePath;
        }

        /// <summary>
        /// Get connection
        /// </summary>
        /// <param name="name"></param>
        /// <param name="defaultValue"></param>
        /// <returns></returns>
        public static string GetConnection(string name, string defaultValue)
        {
            return ConfigurationManager.ConnectionStrings[name] == null ? defaultValue : ConfigurationManager.ConnectionStrings[name].ConnectionString;
        }
    }