Troubleshooting Exceptions: System.Data.NoNullAllowedException
If you use the navigation buttons to move through the records of a database table on a data form, this exception may be thrown with the additional information, "Column 'Column' does not allow nulls." This behavior occurs because the primary key or the "not NULL" column of the database table was not selected in the Data Form Wizard. If the primary key or the "not NULL" column of the database is not selected in the Data Form Wizard when you create the data form, the Add- Creates a new record option is not disabled. To work around this problem, select the following columns of the selected table when you add a data form by using the Data Form Wizard: the primary column and a column that does not permit NULLs.