стиль
<Style x:Key="StyleButton1">
            <Style.Triggers>
                <Trigger Property="local:ImageFoto.CamIsOn" Value="true">
                    <Setter Property="Button.IsEnabled" Value="true"></Setter>
                </Trigger>
                
            </Style.Triggers>
        </Style>


применяем стиль
            <Button Name="bGetFoto" FontSize="16" Click="bGetFoto_Click" IsEnabled="False" Style="{StaticResource StyleButton1}" >Сфотографировать
            </Button>
  

зависимое свойство
 public static readonly DependencyProperty CamIsOnProperty =
        DependencyProperty.Register("CamIsOn", typeof(bool), typeof(ImageFoto),new PropertyMetadata(false));
   

        public bool CamIsOn
        {
            get { return (bool)this.GetValue(CamIsOnProperty); }
            set { this.SetValue(CamIsOnProperty, value); }
        }

<Button Name="bGetFoto" FontSize="16" Click="bGetFoto_Click" IsEnabled="{Binding Path=CamIsOn RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=local:ImageFoto, AncestorLevel=1}}" >Сфотографировать
            </Button>