WPF绑定并转换

public class DataDemo:INotifyPropertyChanged
    {
        private DateTime dateTime;
        public DataDemo()
        {
            dateTime = DateTime.Now;
        }
        public DateTime TheDateTime {
            get { return dateTime; }

            set { dateTime = value; }

        }
        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged(string info)
        {
            PropertyChanged?.Invoke(this,new PropertyChangedEventArgs(info));
        }
    }

  public class ConverterDemo : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            var date = (DateTime)value;
            switch (targetType.Name)
            {
                case "String":
                    return date.ToString("F",culture);
                case "Brush":
                    return Brushes.Blue;
                default:
                    return value;
            }
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return null;
        }
    }

<StackPanel>
        <StackPanel.Resources>
            <local:DataDemo x:Key="DataDemos"/>
            <local:ConverterDemo x:Key="ConverterDemos"/>
            <Style TargetType="TextBlock">
                <Setter Property="FontSize" Value="24"/>
                <Setter Property="Margin" Value="5"/>
            </Style>
        </StackPanel.Resources>
        <StackPanel.DataContext>
            <Binding Source="{StaticResource DataDemos}"/>
        </StackPanel.DataContext>
        <TextBlock Text="为转换的数据:"/>
        <TextBlock Text="{Binding Path=TheDateTime}"/>
        <TextBlock Text="转换的数据:"/>
        <TextBlock Foreground="{Binding Path=TheDateTime,Converter={StaticResource ConverterDemos}}">
            <TextBlock.Text>
                <Binding Path="TheDateTime"
                         Converter="{StaticResource ConverterDemos}"/>
            </TextBlock.Text>
        </TextBlock>
    </StackPanel>