WPF Binding

slider.Value를 바인딩 할 때 지정한 Converter를 사용하라

라는 의미

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Grid.Resources>
            <local:Light x:Key="LightConvert"/>
        </Grid.Resources>
        <StackPanel>
            <TextBlock Text="TextBlock"/>
            <TextBox Text="TextBox" Background="{Binding Value, ElementName=slider, Converter={StaticResource LightConvert}}"/>
            <ProgressBar Value="50" Width="60" Height="20"/>
            <Slider Value="5" Width="60" x:Name="slider"/>
            <PasswordBox Password="Secret"/>
        </StackPanel>
    </Grid>
</Window>

namespace WpfApp1
{
  public class Light : IValueConverter
  {
    public object Convert(object value,
      Type targetType, object parameter, CultureInfo cluture)
    {
      
      var iValue = (double)value;
      if (iValue > 7)
      {
        return "Red";
      }
      else if (iValue < 7 && iValue >= 4)
      {
        return "Yellow";
      }
      else
      {
        return "Green";
      }
    }
  }
}

"WPF MVVM 일주일 만에 배우기" 를 참고 하였습니다