Hi Patrick,
Thank you for contacting Syncfusion support.
Yes. You need to use CONCAT function instead of adding directly through “+” operator. Kindly use the below expression to join string and integer.
Expression:
IF([LayerNum]=0,[Auberhalb],CONCAT([Schicht],CHAR([LayerNum])))
Please do let us know if you need any further assistance on this.
Regards,
Umapathy S.