@praveen @brian @tony
When I use a File type column, there are some certain cases that I don’t want the users to upload files other than PDF, DOC or restrict the upload of certain file types like PNG, JPG etc. To verify this shall be as easy as constructing a Valid_if expression like:
".PDF" = UPPER(RIGHT([FileColumnName],4))
However, whatever way you construct this kind of expression to ensure the file type, the expression evaluates to a null value (empty string) and therefore always eval to FALSE.