Key attribute can be used only on a tag contained in an IDictionary type property?

Question

I don't know what this means, but with this bit of XAML in my Windows Phone app (C#), it's giving me the error "Key attribute can be used only on a tag contained in an IDictionary type property."

<local:Settings x:Key="appSettings"></local:Settings>

Any ideas?

EDIT: Using this as a reference: http://msdn.microsoft.com/en-us/library/ff769510(v=vs.92).aspx

As requested:

<phone:PhoneApplicationPage
    x:Class="Google_.Settings"
    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:local="clr-namespace:Google_"

    FontFamily="{StaticResource PhoneFontFamilyNormal}"
    FontSize="{StaticResource PhoneFontSizeNormal}"
    Foreground="{StaticResource PhoneForegroundBrush}"
    SupportedOrientations="Portrait" Orientation="Portrait"
    mc:Ignorable="d" d:DesignHeight="768" d:DesignWidth="480"
    shell:SystemTray.IsVisible="True">

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

        <!--TitlePanel contains the name of the application and page title-->
        <StackPanel x:Name="TitlePanel" Margin="12,20,0,25">
            <TextBlock x:Name="ApplicationTitle" Text="GOOGLE+" Style="{StaticResource PhoneTextNormalStyle}"/>
            <TextBlock x:Name="PageTitle" Text="settings" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
        </StackPanel>
        <CheckBox Content="Warning on exit" Grid.Row="1" Height="72" HorizontalAlignment="Left" Margin="12,0,0,0" Name="exitAlert" VerticalAlignment="Top" Width="456" IsChecked="{Binding Source={StaticResource appSettings}, Path=CheckBoxSetting, Mode=TwoWay}"/>
        <!--<CheckBox Content="Enable location data" Grid.Row="1" Height="72" HorizontalAlignment="Left" Margin="12,72,0,0" Name="location" VerticalAlignment="Top" Width="456" IsChecked="True" />
        <CheckBox Content="Lock orienation to portrait" Grid.Row="1" Height="72" HorizontalAlignment="Left" Margin="12,144,0,0" Name="orientation" VerticalAlignment="Top" Width="456" />-->

        <local:Settings x:Key="appSettings"></local:Settings>

    </Grid>

</phone:PhoneApplicationPage>

Answer 1

x:Key specifies the key of an item in a dictionary.

You can only use it in a tag that is going into a dictionary, such as inside a <Resources> collection.