public void atualiza_grid()
        {
            classDentista den = new classDentista();
            dataGridView1.Rows.Clear();
            arr.Clear();
            try
            {

                arr = den.buscar(txtDentista.Text);
                for (int i = 0; i < arr.Count; i++)
                {
                    dataGridView1.Rows.Add();
                    dataGridView1[0, i].Value = ((classDentista)arr[i]).Nome;
                    dataGridView1[1, i].Value = ((classDentista)arr[i]).Cro;
                    dataGridView1[2, i].Value = ((classDentista)arr[i]).Cpf;

                }
            }
            catch (Exception e)
            {
                throw e;
            }
        }