您是否尝试过MSDN?

http://msdn.microsoft.com/en-us/library/system.windows.forms.toolstripsplitbutton.createdefaultdropdown.aspx#Y20 [

Have you tried MSDN?

http://msdn.microsoft.com/en-us/library/system.windows.forms.toolstripsplitbutton.createdefaultdropdown.aspx#Y20[^]