Sự kiện SelectedIndexChanged của combobox trong DataGridView

private void dataGridView1_EditingControlShowing(object sender,
DataGridViewEditingControlShowingEventArgs e)
{
if (dataGridView1.CurrentCell.ColumnIndex == 0)
{
ComboBox comboBox = e.Control as ComboBox;
comboBox.SelectedIndexChanged += new EventHandler(comboBox_SelectedIndexChanged);
}
}

void comboBox_SelectedIndexChanged(object sender, EventArgs e)
{
int selectedIndex = ((ComboBox)sender).SelectedIndex;
MessageBox.Show("Selected Index = " + selectedIndex);
}