private async Task <TokenEntity> GetToken(CloudTable table, string token)
{
//todo cache lochalle
var filter = string.Format("({0}) AND ({1})",
TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.Equal, _class),
TableQuery.GenerateFilterCondition("RowKey", QueryComparisons.Equal, token));
TableQuerySegment <TokenEntity> result = await table.ExecuteQuerySegmentedAsync(new TableQuery <TokenEntity>().Where(filter), null);
return(result.Single());
}