sort event not toggling asc and desc

Hi Yong, 

Please refer to our documentation and follow the step-by-step guide there on how to enable sorting. There is also a very helpful example of Grid sorting:
https://www.telerik.com/kendo-react-ui/components/grid/sorting/ 

If you are making multiple data operations, we recommend using process and onDataStateChange event, as shown here: https://www.telerik.com/kendo-react-ui/components/grid/data-operations/local-operations/ 

The arrows should appear automatically if the sort is used correctly, they are based on the information passed to the sort prop of the Grid:

https://www.telerik.com/kendo-react-ui/components/grid/api/GridProps/#toc-sort

If after following the steps in our documentation, there still are issues/unclear things, please send us an example of the Grid you want to implement sorting to, so that we can debug the code.

Hope this is helpful.

Regards,
Krissy
Progress Telerik