Situation:
My database has a table in which records can refer to other records in the same table. Each record has a unique numeric identifier (auto-identifier column) and a column with a null value IDRef, which may contain the identifier of the record to be referenced.
Now, in my C # Windows Forms application, I use a DataGridView to allow the user to edit records in a table. It can add, edit or delete items. I have a typed DataSet for storing data and a corresponding TableAdapter for loading data from the database and performing updates. The DataGridView is bound to a BindingSource, which uses a typed DataSet as a data source.
For the column, IDRefI added a ComboBox column, which fills its values from the same BindingSource as the DataGridView itself. This means that the ComboBox is always updated with the number of records.
Problem:
I am showing a column IDin a DataGridView. When adding new rows, clicking in the corresponding row of the DataGridView, the identifier value is automatically filled with negative values. The final value of the auto-identifier is calculated only after saving the changes to the database using the TableAdapter.
Now, when I drop out of ComboBox for a column IDRef, I can select previously existing records (e.g. 101, 102, etc.), but I can also select the records that were added after the last update of the database (e.g. -1 , -2, -3).
Now: after using the TableAdapter method Updateto save changes to the database, these negative identifiers no longer exist - I refer to nonexistent records (in my case, this leads to a foreign key constraint error).
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