Data in the number type in Oracle uses the As string to get a value of NULL

1, if the data run-time type (and the database field type is the same) is not a string type, such as number/date, etc., will be DS. Tables[0]. ROWS[I][J] When calling as string, regardless of

If this field has a value, it will get null.

As String only converts an object with a run-time type of string to a string, and if the runtime type is not a string, it gets null without an error.

2, if the data found from the database may be null, the convert.tostring () class conversion is called.

If it is not NULL, it is called directly. ToString () on the line.