updating datagrid in c' using oledb

Question

Hi all

im trying to update a datagrid table and below is the code i have been using but every time i run it i get an error:

Error:

System.NullReferenceException was unhandled

  HResult=-2147467261

  Message=Object reference not set to an instance of an object.

  Source=WindowsFormsApplication6

private void button6_Click(object sender, EventArgs e)

        {

           

                string sql = "Insert into [Sheet1$](first,last) Values(`" + textBox1.Text + "`, `" + textBox2.Text + "`)";

                connect.Open();

                OleDbDataAdapter adap = new OleDbDataAdapter(sql, connect);

                adap.SelectCommand.ExecuteNonQuery();

                adap.Dispose();

                connect.Close();

                connect.Dispose();

                MessageBox.Show("Saved");

                

               

                

            }