DataSet中存在二个表:BMainType(BMainTypeID,BMainTypeName),
                    BMinorType(BMainTypeID,BMinorTypeID,BMinorTypeName);
代码:     Form_Load(object sender, EventArgs e)
         {
            DataTable dt=new DataTable();
            dt=DS.Tables["BMinorType"];
            dataGridView1.DataSource = dt; 
            dataGridView1.Columns.Remove("BMainTypeID");
            DataGridViewComboBoxColumn List = new DataGridViewComboBoxColumn()
            List.DisplayIndex = 2;
            List.HeaderText = "BMainType";
            List.DataPropertyName = "BMainTypeID";
            List.DataSource = DS.Tables["BMainType"];
            List.DisplayMember = "BMainTypeName";
            List.ValueMember = "BMainTypeID";  
            dataGridView1.Columns.Add(List);
         }
请问这样绑定后用SqlDataAdapter.update((DataTable)dataGridView1.DataSource )为什么不能将添加数据添加入数据库中呀??