rework dlna project

RSSDP/IEnumerableExtensions.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Rssdp.Infrastructure
+{
+	internal static class IEnumerableExtensions
+	{
+		public static IEnumerable<T> SelectManyRecursive<T>(this IEnumerable<T> source, Func<T, IEnumerable<T>> selector)
+		{
+			if (source == null) throw new ArgumentNullException("source");
+			if (selector == null) throw new ArgumentNullException("selector");
+
+			return !source.Any() ? source :
+					source.Concat(
+							source
+							.SelectMany(i => selector(i).EmptyIfNull())
+							.SelectManyRecursive(selector)
+					);
+		}
+
+		public static IEnumerable<T> EmptyIfNull<T>(this IEnumerable<T> source)
+		{
+			return source ?? Enumerable.Empty<T>();
+		}
+	}
+}