添加菜单图标

ToolStripMenuItem type1 = new ToolStripMenuItem(".pdf");
type1.CheckOnClick = true;
type1.Image = this.toolIcon.Images[5];
type1.Checked = true;
this.toolStripDropDownButton2.DropDownItems.Add(type1);

是不是显示了Check项就不能显示图标？怎么我怎么加都不行呢？
[解决办法]

type1.CheckedChanged += type1_CheckedChanged;

void type1_CheckedChanged(object sender, EventArgs e)
{
  toolStripDropDownButton2.ShowDropDown();
}