public class AuthenticationConverter : IValueConverter
02.    {
03. 
04. 
05.        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
06.        {
07.            if ((bool)value == true)
08.            {
09.                return Visibility.Visible;
10.            }
11.            else
12.            {
13.                return Visibility.Collapsed;
14.            }
15.        }
16.        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
17.        {
18.            throw new NotImplementedException();
19.        }
20.    }

class UserState
02.    {
03.        public bool userLogInOrOut { get; set; }
04. 
05.        public UserState()
06.        {
07.            userLogInOrOut = true;
08.        }
09.    }

1.<UserControl.Resources>
2.        <local:AuthenticationConverter x:Key="AuthConverter"/>
3.        <state:UserState x:Key="userState"/>
4.    </UserControl.Resources>

<Visibility="{Binding Path=userLogInOrOut, Source={StaticResource userState}, Converter={StaticResource AuthConverter}}"/>

public MainPage()
        {
            InitializeComponent();
            UserState state = new UserState();
            state.userLogInOrOut = false;
           
        }

<UserControl 
  x:Class="GuestBook.MainPage"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:navigation="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Navigation" 
  xmlns:uriMapper="clr-namespace:System.Windows.Navigation;assembly=System.Windows.Controls.Navigation"
  xmlns:dataControls="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data.DataForm.Toolkit" 
  xmlns:login="clr-namespace:GuestBook.LoginUI"
  xmlns:local="clr-namespace:GuestBook.Helpers"
  xmlns:state="clr-namespace:GuestBook"
  xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
  mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480" xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk" Loaded="UserControl_Loaded">
    
    <UserControl.Resources>
        <local:AuthenticationConverter x:Key="AuthConverter"/>
        <state:UserState x:Key="userState"/>
    </UserControl.Resources>
    
        <Grid x:Name="LayoutRoot" Style="{StaticResource LayoutRootGridStyle}">

        <Border x:Name="ContentBorder" Style="{StaticResource ContentBorderStyle}">
            <navigation:Frame x:Name="ContentFrame" Style="{StaticResource ContentFrameStyle}" 
                              Source="/Home" Navigated="ContentFrame_Navigated" NavigationFailed="ContentFrame_NavigationFailed">
                <navigation:Frame.UriMapper>
                    <uriMapper:UriMapper>
                        <uriMapper:UriMapping Uri="" MappedUri="/Views/Home.xaml"/>
                        <uriMapper:UriMapping Uri="/{pageName}" MappedUri="/Views/{pageName}.xaml"/>
                    </uriMapper:UriMapper>
                </navigation:Frame.UriMapper>
            </navigation:Frame>
        </Border>

        <Grid Style="{StaticResource NavigationOuterGridStyle}">
            <Grid x:Name="NavigationGrid" Style="{StaticResource NavigationGridStyle}">

                <Border x:Name="BrandingBorder" Style="{StaticResource BrandingBorderStyle}">
                    <StackPanel x:Name="BrandingStackPanel" Style="{StaticResource BrandingStackPanelStyle}">

                        <ContentControl Style="{StaticResource LogoIcon}"/>
                        <TextBlock x:Name="ApplicationNameTextBlock" Style="{StaticResource ApplicationNameStyle}" 
                               Text="{Binding Strings.ApplicationName, Source={StaticResource ApplicationResources}}"/>

                    </StackPanel>
                </Border>

                <Border x:Name="LinksBorder" Style="{StaticResource LinksBorderStyle}">
                    <StackPanel x:Name="LinksStackPanel" Style="{StaticResource LinksStackPanelStyle}">

                        <HyperlinkButton x:Name="Link1" Style="{StaticResource LinkStyle}" 
                                     NavigateUri="/Home" TargetName="ContentFrame" Content="{Binding Path=Strings.HomePageTitle, Source={StaticResource ApplicationResources}}"/>

                        <Rectangle x:Name="Divider1" Style="{StaticResource DividerStyle}"/>

                        <HyperlinkButton x:Name="Link2" Style="{StaticResource LinkStyle}" 
                                     NavigateUri="/About" TargetName="ContentFrame" Content="{Binding Path=Strings.AboutPageTitle, Source={StaticResource ApplicationResources}}"/>
                        <Rectangle x:Name="Divider2" Style="{StaticResource DividerStyle}"/>

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
                       <HyperlinkButton x:Name="Link3" Style="{StaticResource LinkStyle}" 
                                     NavigateUri="/GuestBookPage" TargetName="ContentFrame" Content="{Binding Path=Strings.GuestBookPageTitle, Source={StaticResource ApplicationResources}}" Visibility="{Binding Path=userLogInOrOut, Source={StaticResource userState}, Converter={StaticResource AuthConverter}}"/>

Вот тут я привязываюсь к классу UserState  а точней к свойству userLogInOrOut  через ресурс userState.  Конвертер опредиляет значение свойство и возвращает Visibility;
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

                    </StackPanel>
                </Border>

            </Grid>

            <Border Style="{StaticResource LoginContainerStyle}">
                <login:LoginStatus x:Name="loginStatus"/>
            </Border>
        </Grid>
    </Grid>

</UserControl>