How to make sure the property exists and have a value ...Want to set other properties in data transform depends on  the property exists and has a value(not null or not empty).

What functions and which expression do this correctly ?

@PropertyHasValue(D_LookUpAccount.PHONE)  -- will this check for null ? what value will it return for null or empty property ?

@notEquals(D_LookUpAccount.PHONE, "")  -- how to check null with this function...is this correct "null" ? 

PropertyExists("D_LookUpAccount.PHONE") -- this function doesn't allow D page --throwing error 

Pls type any expression that checks all of these