RAISERROR with severity level below 10 are not catched by ADO framework. To fix it simply raise severity level to 10 or above or you can instead use THROW statement which has severity level of 16 by default and will always be catched by the ADO framework (C#).
RAISERROR(‘Your Error Message’, ‘Severity Level’, ‘State Level’)
Set Severity Level to 16
Set State Level to 1
Note that RAISERROR does not stop execution. It is recommend to use THROW statement inst5ead to raise error and stop execution.