WPF RadioButton Gray Out

<Window x:Class="WpfAppExamples.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="RadioButtonSample" Height="150" Width="250">
    <Window.Resources>
        <Style TargetType="RadioButton" BasedOn="{StaticResource {x:Type RadioButton}}">
            <Style.Triggers>
                <Trigger Property="IsChecked" Value="False">
                    <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                </Trigger>
            </Style.Triggers>
        </Style>
    </Window.Resources>
    <StackPanel Margin="10">
        <Label FontWeight="Bold">Are you ready?</Label>
        <RadioButton GroupName="testing">Yes</RadioButton>
        <RadioButton GroupName="testing">No</RadioButton>
        <RadioButton IsChecked="True" GroupName="testing">Maybe</RadioButton>
    </StackPanel>
</Window>

public bool IndicatorState {
            get {
                return m_IndicatorState;
            }
            private set {
                SetProperty(ref m_IndicatorState, value);
            }
        }

<RadioButton x:Name="RadioButton2" />
<TextBox BorderThickness="0" IsEnabled="{Binding IsChecked, ElementName=RadioButton2}" />

   ProcessStartInfo psInfo = new ProcessStartInfo {
                     FileName = 
"https://teknic.com/files/downloads/Clearpath-SC%20User%20Manual.pdf",
                     UseShellExecute = true
                 };
             Process.Start(psInfo);