如何仅在关闭子窗体后执行代码？C#

public event EventHandler ChildFormClosed;

private void ChildForm_FormClosed(object sender, FormClosedEventArgs e)
{
    ChildFormClosed?.Invoke(this, EventArgs.Empty);
}

private void OpenChildFormButton_Click(object sender, EventArgs e)
{
    ChildForm childForm = new ChildForm();
    childForm.ChildFormClosed += ChildForm_Closed;
    childForm.Show();
}

private void ChildForm_Closed(object sender, EventArgs e)
{
    // 在子窗体关闭后执行的代码
}