WPF的转换器中使用Brush应注意问题

1、Brushes用错了命名空间将导致程序无法正确工作。笔者曾写了一个flag值转换为相应的Brush，由于不小心Using了一个错误的命名空间（System.Drawing）导致Xaml文件界面元素Fill绑定属性总出不来应有的效果。最后费了好大劲才发现，替换为正确的命名空间（System.Windows.Media）后立马就解决了。特此留下随笔备忘。

2、下面是一个IMultiValueConverter的例子：

<Window x:Class="WpfApplication16.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:my="clr-namespace:WpfApplication16" Title="Window1" Height="300" Width="300"> <Window.Resources> <my:RgbConverter x:Key="RgbConverter" /> </Window.Resources> <Window.Background> <SolidColorBrush> <SolidColorBrush.Color> <MultiBinding Converter="{StaticResource RgbConverter}"> <Binding Path="Value" ElementName="redSlider" /> <Binding Path="Value" ElementName="greenSlider" /> <Binding Path="Value" ElementName="blueSlider" /> </MultiBinding> </SolidColorBrush.Color> </SolidColorBrush> </Window.Background> <StackPanel> <Slider Minimum="0" Maximum="255" x:Name="redSlider" /> <Slider Minimum="0" Maximum="255" x:Name="greenSlider" /> <Slider Minimum="0" Maximum="255" x:Name="blueSlider" /> </StackPanel> 
</Window> 

public class RgbConverter : IMultiValueConverter 
{ #region IMultiValueConverter Members public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture) { var r = System.Convert.ToByte(values[0]); var g = System.Convert.ToByte(values[1]); var b = System.Convert.ToByte(values[2]); return Color.FromRgb(r, g, b); } public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture) { throw new NotImplementedException(); } #endregion 
} 

 3、多值参数如何处理，譬如：希望value为真时返回ConvertParameter指定R,G,B的颜色值Brush，否则返回透明Brush。

<Border Grid.ColumnSpan="3" BorderBrush="{Binding Converter={StaticResource BoolToSolidColorBrushConverter}, ConverterParameter='255,0,0', Path=IsInclusive}" BorderThickness="2"><Image Source="{Binding Image}" Opacity="{Binding ImageOpacity}" />
</Border>

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{Brush result = Brushes.Red;if (parameter != null){string[] rgb = parameter.ToString().Split(',');if (rgb.Length == 3){byte r = 0;byte.TryParse(rgb[0], out r);byte g = 0;byte.TryParse(rgb[1], out g);byte b = 0;byte.TryParse(rgb[2], out b);result = new SolidColorBrush(Color.FromRgb(r, g, b));}}if (value == null) return Brushes.Transparent;string valueString = value.ToString();if (value.ToString() == "1"){valueString = "True";}else if (value.ToString() == "0"){valueString = "False";}bool boolValue = false;if (!bool.TryParse(valueString, out boolValue)){boolValue = false;}if (boolValue) return result;return Brushes.Transparent;
}