[Modify] Add it

websocket-sharp/Net/QueryStringCollection.cs

@@ -61,6 +61,17 @@ namespace WebSocketSharp.Net
 
     #endregion
 
+    #region Private Methods
+
+    private static string urlDecode (string s, Encoding encoding)
+    {
+      return s.IndexOfAny (new[] { '%', '+' }) > -1
+             ? HttpUtility.UrlDecode (s, encoding)
+             : s;
+    }
+
+    #endregion
+
     #region Public Methods
 
     public static QueryStringCollection Parse (string query)