I have a datagridview with a dataTable as the dataSource. The user can add new rows to the datadridview, but I dont display the primary key column (for obvious reasons) and set it to .visible = false. When I need to update the information in the datagridview to the database, I use the sqlClient.SqlCommandBuilder to then update the underlying datasource (the dataTable mentioned above). Now, because the hidden column is the primary key, I loop through the datagridview and programically add the required primary key field to each new row that does not already contain a primary key (user added rows). This works great 95% of the time... The problem is when the user somehow gives focus at some point (any point) to that bottom row on the datagridview, below their added rows, that is used to add new rows. The update command gives me an error stating that it cannot insert null into the primary key field, even though when checking all the values in every row, it is definitely NOT null for any of them. I have tried to trap for row.isNewRow (as the field never shows null) and deleting that row, but I get an error stating I can not delete an uncommitted row. If the focus is never given to that empty row beneath the existing rows and user added rows, the update works fine. What is going on?!