Communication control property from internal control

I have a control that contains another control. InnerControl contains some property like ButtonVisibility. Simplified InnerControl code sample below

public class InnerControl : ControlBase
{
    //...
    public Visibility ButtonVisibility
    {
        get { return (Visibility)GetValue(ButtonVisibility); }
        set { SetValue(ButtonVisibility, value); }
    }

    public static readonly DependencyProperty ButtonVisibility =
        DependencyProperty.Register(
            "ButtonVisibility",
            typeof (Visibility),
            typeof (InnerControl),
            new PropertyMetadata(Visibility.Collapsed));
}

      

        
        
        
      

    

This is the MainControl code which contains the InnerControl as a dependency property

public class MainControl : ControlBase
{
    //...
    public InnerControl MyInner
    {
        get { return (InnerControl) GetValue(MyInnerProperty); }
        set { SetValue(MyInnerProperty, value); }
    }

    public static readonly DependencyProperty MyInnerProperty =
        DependencyProperty.Register(
            "MyInner",
            typeof (InnerControl),
            typeof (MainControl),
            new PropertyMetadata(null, OnMyInnerPropertyChanged));

    private static void OnMyInnerPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        //...
    }
}

      

        
        
        
      

    

I have two different templates for these controls in Generic.xaml

<Style TargetType="local:InnerControl">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="local:InnerControl">
                <Grid x:Name="ContainerGrid">
                    <!-- some markup -->
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

<Style TargetType="local:MainControl">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="local:MainControl">
                <Grid x:Name="RootGrid">

                    <Button x:Name="MyButton" Visibility="{TemplateBinding ???}"/>

                    <ContentControl x:Name="MyInnerControl" Content="{TemplateBinding MyInner}" />

                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

      

        
        
        
      

    

This is how I can use these controls

<controls:MainControl>
    <controls:MainControl.MyInner>
        <controls:InnerControl ButtonVisibility="Visible">
            <!-- some markup -->                
        </controls:InnerControl>
    </controls:MainControl.MyInner>

    <!-- some markup -->
</controls:MainControl>

      

        
        
        
      

    

I need to change the state of mine MainControl

after clicking a button. Therefore, it is in the template MainControl

.

So, can any body give me advice on how to link ButtonVisibility

from MyInner

with MyButton

to MainControl

?