用一个ProcessBar显示电量，低于20%时候,ForeGround为红色，否则为绿色，
页面使用了MVVM绑定到了ViewModel, ProcessBar XAML为
<ProgressBar Maximum="100" Value="{Binding RemainPercent}" Foreground="{Binding RemainPercent, Converter={StaticResource ForgroundConverter}}" ></ProgressBar>
其中 ForgroundConverter为资源的key
xmlns:converter ="clr-namespace:XXX.XXX"
<UserControl.Resources> <converter:PercentForgroundConverter x:Key="ForgroundConverter"/> </UserControl.Resources>
PercentForgroundConverter 为实现了IValueConverter的类，方法如下，
Brushes的命名空间为System.Windows.Media。
public class PercentForgroundConverter:IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { double percent = (double)value; if (percent<=20) { return Brushes.Red; } return Brushes.Green; } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { throw new NotImplementedException(); } }
原文：http://www.cnblogs.com/pangkang/p/5874629.html