winform中datagridview有一列DataGridViewComboBoxColumn，如何选中某一项才触发dataGridView1_EditingControlShowing事件

datagridview中有一列是下拉框DataGridViewComboBoxColumn，如何选中下拉框中的某一项才触发dataGridView1_EditingControlShowing事件，而不是一点击下拉框就触发。

  private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            DataGridView dgv1 = (DataGridView)sender;
            if (dgv1.CurrentCell.GetType().Name == "DataGridViewComboBoxCell" && dgv1.CurrentCell.RowIndex != -1)
            {
                //给这个DataGridViewComboBoxCell加上下拉事件
                (e.Control as ComboBox).SelectedIndexChanged += new EventHandler(dgvComboBox1_SelectedIndexChanged);
            }
        }

private void dgvComboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {

            ComboBox combox = sender as ComboBox;

            //这里比较重要
            combox.Leave += new EventHandler(dgvComboBox1_Leave);
            try
            {
                //在这里就可以做值是否改变判断
                if (combox.SelectedItem != null && combox.SelectedItem.ToString() != "")
                {
                    string selectItem = combox.SelectedItem.ToString();
                }

            }
            catch (Exception ex)
            {
                MessageBox.Show(this, "错误:" + ex.Message, "系统提示", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }

        }

        private void dgvComboBox1_Leave(object sender, EventArgs e)
        {
            ComboBox combox = sender as ComboBox;
            combox.SelectedIndexChanged -= new EventHandler(dgvComboBox1_SelectedIndexChanged);
        }

你不是已经添加了selectedchanged事件了，为什么还需要edit事件
你直接在单元格里事件里判断，如果是combo列就return