Datetime comparison for Azure Table Storage REST API

From http://msdn.microsoft.com/en-us/library/dd894027.aspx and http://msdn.microsoft.com/en-us/library/dd894031.aspx:

string.Format("{0} le datetime'{1}'", PropertyName, XmlConvert.ToString(cutoffDate, XmlDateTimeSerializationMode.RoundtripKind))

although obviously this will then need to be UrlEncoded