MyUserControls从MainWindow继承了DataContext，这就是为什么它可以开始使用的原因.当MyUserControl1获得自己的ViewModel时，将成为其DataContext.也许这对您很清楚:)要在绑定中使用MainWindow的DataContext，可以使用RelativeSource或命名Window并使用ElementName

The MyUserControls inherited the DataContext from MainWindow and that's why it works to begin with. When MyUserControl1 get a ViewModel of its own that will be its DataContext. Maybe this was clear to you :) To use the DataContext of the MainWindow in the binding instead you can use RelativeSource or name the Window and use ElementName

<local:MyUserControl Visibility="{Binding ElementName=mainWindow, 
                                          Path=DataContext.MyUserControl1Visibility,
                                          Mode=OneWay,
                                          UpdateSourceTrigger=PropertyChanged}" />