Databinding and INotifyPropertyChanged not working

Question

In my WP7 application, I want to update the ApplicationTitle line on all pages at the same time when something has changed. I was looking for ways to do this, and people are talking about using data binding and the INotifyPropertyChanged interface. However, using the samples I found, I cannot get it to work. I suspect the binding is erroneous, but the error could not be detected.

I have a class called "RegistrationQueue" that has the following code:

    public void Gem()
    {
        var settings = IsolatedStorageSettings.ApplicationSettings;

        if (settings.Contains("regqueue"))
        {
            settings["regqueue"] = _registreringsListe;
        }
        else
            settings.Add("regqueue", _registreringsListe);

        AppTitle = "LOGIMATIC A/S - " + _registreringsListe.Count + " registreringer i kø";
    }

And this:

    private string _AppTitle;

    // Declare the PropertyChanged event.
    public event PropertyChangedEventHandler PropertyChanged;

    // Create the property that will be the source of the binding.
    public string AppTitle
    {
        get { return _AppTitle; }
        set
        {
            _AppTitle = value;
            // Call NotifyPropertyChanged when the source property 
            // is updated.
            NotifyPropertyChanged("AppTitle");
        }
    }


    // NotifyPropertyChanged will raise the PropertyChanged event, 
    // passing the source property that is being updated.
    public void NotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this,
                new PropertyChangedEventArgs(propertyName));
        }
    }

This is basically a copy / paste from MSDN, as far as I remember.

On one of my XAML pages, I wrote this:

<TextBlock x:Name="ApplicationTitle" Text="{Binding AppTitle, Mode=OneWay}" Style="{StaticResource PhoneTextNormalStyle}" />

And I thought it would work, but it is not. What am I doing wrong here?

Full XAML for the page:

<phone:PhoneApplicationPage 
    x:Class="FotoDokUdkast.loginScreen"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
    xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:toolkit="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone.Controls.Toolkit"
    mc:Ignorable="d" FontFamily="{StaticResource PhoneFontFamilyNormal}"
    FontSize="{StaticResource PhoneFontSizeNormal}"
    Foreground="{StaticResource PhoneForegroundBrush}"
    SupportedOrientations="PortraitOrLandscape" Orientation="Portrait"
    shell:SystemTray.IsVisible="True" d:DesignHeight="696" d:DesignWidth="480">

    <!--LayoutRoot is the root grid where all page content is placed-->
    <Grid x:Name="LayoutRoot" Background="Black">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <!--TitlePanel contains the name of the application and page title-->
        <StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">
            <!--<TextBlock x:Name="ApplicationTitle" Text="LOGIMATIC A/S" Style="{StaticResource PhoneTextNormalStyle}"/>-->
            <TextBlock x:Name="ApplicationTitle" Text="{Binding Path=AppTitle, Mode=OneWay}" Style="{StaticResource PhoneTextNormalStyle}"/>
            <TextBlock x:Name="PageTitle" Text="FotoDok 0.5b " Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
        </StackPanel>

        <!--ContentPanel - place additional content here-->
        <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0" Background="Black">
            <TextBlock Height="30" HorizontalAlignment="Left" Margin="6,6,0,0" Name="textBlock1" Text="Et Logimatic program" VerticalAlignment="Top" Width="444" />
            <toolkit:ListPicker Name="pickerProject" Margin="9,42,15,0" Header="Vælg projekt" ListPickerMode="Normal" ItemCountThreshold="0" FullModeHeader="Vælg projekt" Height="97" VerticalAlignment="Top" />
            <Button Content="Log ind" Height="72" HorizontalAlignment="Left" Margin="6,337,0,0" Name="btnLogin" VerticalAlignment="Top" Width="444" Click="btnLogin_Click" />
            <toolkit:ListPicker Header="Vælg bruger" Margin="9,145,15,292" Name="pickerUser" ListPickerMode="Normal" ItemCountThreshold="0" FullModeHeader="Vælg bruger" />
        </Grid>
    </Grid>

    <!--Sample code showing usage of ApplicationBar-->
    <phone:PhoneApplicationPage.ApplicationBar>
        <shell:ApplicationBar IsVisible="True" IsMenuEnabled="True">
            <shell:ApplicationBarIconButton IconUri="Images/appbar.sync.rest.png" Text="Opdater projekter" Click="ApplicationBarIconButtonOpdater_Click"/>
            <shell:ApplicationBarIconButton IconUri="Images/appbar.delete.rest.png" Text="Slet projekter" Click="ApplicationBarIconButtonSlet_Click"/>
            <shell:ApplicationBarIconButton IconUri="Images/appbar.feature.email.rest.png" Text="Registreringer i kø" Click="ApplicationBarIconButtonRegistrering_Click"/>
            <shell:ApplicationBarIconButton IconUri="Images/appbar.feature.settings.rest.png" Text="Tilpas opsætning" Click="ApplicationBarIconButtonSettings_Click"/>

        </shell:ApplicationBar>
    </phone:PhoneApplicationPage.ApplicationBar>

</phone:PhoneApplicationPage>

"DataContext =" RegistreringsKø ";" XAML (loginscreen.cs)

Answer 1

, . , DataContext, TextBlock, , AppTitle. , , AppTitle.

Answer 2

, , , INotifyPropertyChanged ?

, . , : -)

- - , ?

Answer 3

I did not use the datacontext correctly. I wrote ApplicationTitle.Text = "RegistreringsKø" Which, of course, was to be an instance of an object.

So, in my case, DataContext = Registration.getInstance();I decided.