after reading an excel I need to multiply column (0) by -1 I did it with assign row (0) = Convert.ToDouble (Convert.ToInt32 (row (0)) * -1), but “error” conversion from type "comes out DBNull “to type” Double “is not valid” how to solve it?
Make sure that row(0) value is not empty. it should contain some value before conversion.
check the data in the column is null in the initial part like
if true don’t do the action , if not ,do the multiplication