我猜您正在尝试将窗体停靠在面板中，并且将其从面板中拉出时必须是窗体.
检查此链接.希望它能解决.
http://documentation.devexpress.com/#WindowsForms/CustomDocument1265 [

Hi,

I guess you are trying to dock a form when its in a panel.and when its pulled from the panel, it must be a form.
check this link .Hope it works out.
http://documentation.devexpress.com/#WindowsForms/CustomDocument1265[^]