[Question] Why do I have to move data to another record during update when using textbox to bind data?

The four text boxes are bound to the carno, name, address, and make of tblcustomer (visual binding is used)
The Edit button is used to load data, and the Save button is used to save data. It is very simple and simplified as follows:

Private   Void Btnedit_click ( Object Sender, system. eventargs E)
{
Customerdataset1.clear ();
Sqldataadapter1.fill (mermerdataset1 );
}



Private   Void Btnsave_click ( Object Sender, system. eventargs E)
{
Sqldataadapter1.update (mermerdataset1 );
MessageBox. Show ("Database updated!");
}

However, if I modify the text box and press save to update immediately, there is no error, but there is no update in the database; but if I move to the next record and then press save (only the previous record is modified ), the update is successful. Why?