问如何让generic<>使用这个方法--> OpenForm()我不想为每个表单创建方法

EN

public static class UIExtensions
{
  public static void Present(this Form form, Form parent)
  {
    form.MdiParent = parent;
    form.Show();
  }
}

UIDirector directorUI = new UIDirector();
UIActor actorUI = new UIActor();
private void directorToolStripMenuItem_Click(object sender, EventArgs e)
{
    OpenForm(directorUI);
}
private void actorToolStripMenuItem_Click(object sender, EventArgs e)
{
    OpenForm(actorUI);
}

void OpenForm<T>(T frm) where T: Form, new()
{
    if (frm.IsDisposed)
    {
        frm = new T();
    }
    frm.Show();
    frm.MdiParent = this;
}