Spotify.NET/SpotifyAPI.Web/Util.cs

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;

namespace SpotifyAPI.Web
{
  public static class Util
  {
    public static string GetStringAttribute<T>(this T en, string separator = "") where T : struct, IConvertible
    {
      Enum e = (Enum) (object) en;
      IEnumerable<StringAttribute> attributes =
        Enum.GetValues(typeof(T))
        .Cast<T>()
        .Where(v => e.HasFlag((Enum) (object) v))
        .Select(v => typeof(T).GetField(v.ToString(CultureInfo.InvariantCulture)))
        .Select(f => f.GetCustomAttributes(typeof(StringAttribute), false) [0])
        .Cast<StringAttribute>();

      List<string> list = new List<string>();
      attributes.ToList().ForEach(element => list.Add(element.Text));
      return string.Join(separator, list);
    }

    public static long ToUnixTimeMillisecondsPoly(this DateTime time)
    {
      return (long) time.Subtract(new DateTime(1970, 1, 1)).TotalMilliseconds;
    }
  }

  public sealed class StringAttribute : Attribute
  {
    public string Text { get; set; }

    public StringAttribute(string text)
    {
      Text = text;
    }
  }
}