Grid Validation using expression rule

Question

Hello all, 
 I'm trying to validate a grid value which is of type CDT. So lets call this CDT.value, now i'm validating CDT.value by passing it to a Expression Rule in the validations part of the a!gridfield(), but I'm currently getting an error no matter what way I pass this CDT.Value to the Expression rule to evaluate, the error is: Cannot index property 'Value' of type Text into null value of type CDT?list. 
 
 I understand this error is telling me I can't compare a grid (Cdt.value) which is text to a subset of values. Has anyone tried this before? using an expression rule to validate grid data and displaying validation errors accordingly?

Thanks, 
 Nick

vimalkumars · Accepted Answer

When the value passed to the multiple CDT Variable is null and When you try to index a value using the expression "Cdt.value" , you will get this error. You can use index(Cdt, "value", null) instead of Cdt.value