单击“取消”按钮(或右上角的“X”或“Esc”)后如何取消退出特定表单？WPF:View模型:publicclassMyViewModel:Screen{privateCancelCommandcancelCommand;publicCancelCommandCancelCommand{get{returncancelCommand;}}publicMyViewModel(){cancelCommand=newCancelCommand(this);}}publicclassCancelCommand:ICommand{publicCancelCommand(MyViewModelvi