Hi Sorin,
---------
From the VFP help
QUOTE
Evaluates a character expression and returns the result.
EVALUATE(cExpression)
UNQUOTE
As NULL is not an expression, you cannot evaluate it, thus you get an error as desirable, expactable and preventable.
You may want to try EVALUATE("NULL") which is a character expression with the NULL value. This returns NULL.
---------
This is the interpretation of VFP, today.
I prefer to extend the concept:
sExp = 'NULL' is a defined expression
sExp = NULL is a undefined expression, but it is a expression.
sExp = "'A'+1" this is not a expression.
Fabio