[Modify] Add it

websocket-sharp/Ext.cs

@@ -895,6 +895,12 @@ namespace WebSocketSharp
       return ret.Length > 0 ? ret : "/";
     }
 
+    internal static string TrimSlashOrBackslashFromEnd (this string value)
+    {
+      var ret = value.TrimEnd ('/', '\\');
+      return ret.Length > 0 ? ret : value[0].ToString ();
+    }
+
     /// <summary>
     /// Tries to create a new <see cref="Uri"/> for WebSocket with
     /// the specified <paramref name="uriString"/>.