Business rule not working to prevent serial number in a request form

[NayeemSk]

I create a business rule, which needs to prevent a serial number in a request that already exists in a table. Business Rule is not working. Attached the screenshot.

[GlideFather]

Hi @NayeemSk,

I haven't analysed the code but I can see that on the line 7 there is comma (",") instead of dot (".") 

Just a tip: when you want a code review, please share the actual code, not a screenshot, it's easier for reviewers ;))

Let me know if that helped :))