move PocketSharp.Reader

PortablePorts/NReadability/EnumerableExtensions.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace ReadSharp.Ports.NReadability
+{
+  public static class EnumerableExtensions
+  {
+    /// <summary>
+    /// Returns the only one element in the sequence or default(T) if either the sequence doesn't contain any elements or it contains more than one element.
+    /// </summary>
+    public static T SingleOrNone<T>(this IEnumerable<T> enumerable)
+      where T : class
+    {
+      // ReSharper disable PossibleMultipleEnumeration
+
+      if (enumerable == null)
+      {
+        throw new ArgumentNullException("enumerable");
+      }
+
+      T firstElement = enumerable.FirstOrDefault();
+
+      if (firstElement == null)
+      {
+        // no elements
+        return null;
+      }
+
+      T secondElement = enumerable.Skip(1).FirstOrDefault();
+
+      if (secondElement != null)
+      {
+        // more than one element
+        return null;
+      }
+
+      return firstElement;
+
+      // ReSharper restore PossibleMultipleEnumeration
+    }
+  }
+}