Hi Edmund,
Thanks for using Syncfusion products.
Kindly ignore the previous response.
We are facing some issue while setting ValidationRule and ValidationMessage in our sample and we have logged a report regarding this. A support incident to track the status of this defect has been created under your account. Please log on to our support website to check for further updates.
https://www.syncfusion.com/account/login?ReturnUrl=%2fsupport%2fdirecttrac%2fincidents
Please let me know if you have any questions.
Regards,
Saranya.S