Binding to Converter Parameter

问题:

Is it possible to bind to a ConverterParameter in Silverlight 4.0?

For instance I would like to do something like this and bind the ConverterParameter to an object in a ViewModel for instance.

If this is not possible are there any other options?

<RadioButton
  Content="{Binding Path=Mode}"
  IsChecked="{Binding
    Converter={StaticResource ParameterModeToBoolConverter},
    ConverterParameter={Binding Path=DataContext.SelectedMode,ElementName=root}}"
/>

回答1:

Unfortunetly no, you can't bind to a ConverterParameter. There's two options I've used in the past: instead of using a Converter, create a property on your ViewModel (or whatever you're binding to) which does the conversion for you. If you still want to go the Converter route, pass the entire bound object to the converter and then you can do your calculation that way.

回答2:

Another option is to get fancy by creating a custom converter that wraps your other converter and passes in a converter param from a property. As long as this custom converter inherits DependencyObject and uses a DependencyProperty, it can be bound to. For example:

<c:ConverterParamHelper ConverterParam="{Binding ...}">

    <c:ConverterParamHelper.Converter>

        <c:RealConverter/>

    </c:ConverterParamHelper.Converter>

</c:ConverterParamHelper>

回答3:

I know it's an old question but maybe this will be useful to somebody who came across it. The solution I found is as follow:

public class WattHoursConverter : FrameworkElement, IValueConverter
    {

        #region Unit (DependencyProperty)

        /// <summary>
        /// A description of the property.
        /// </summary>
        public string Unit
        {
            get { return (string)GetValue(UnitProperty); }
            set { SetValue(UnitProperty, value); }
        }
        public static readonly DependencyProperty UnitProperty =
            DependencyProperty.Register("Unit", typeof(string), typeof(WattHoursConverter),
            new PropertyMetadata("", new PropertyChangedCallback(OnUnitChanged)));

        private static void OnUnitChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            ((WattHoursConverter)d).OnUnitChanged(e);
        }

        protected virtual void OnUnitChanged(DependencyPropertyChangedEventArgs e)
        {
        }

        #endregion


        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
// you can use the dependency property here
...
}
}

and in your xaml:

<UserControl.Resources>
    <converters:WattHoursConverter x:Key="WattHoursConverter" Unit="{Binding UnitPropFromDataContext}"/>
 </UserControl.Resources>
....
  <TextBlock Grid.Column="1" TextWrapping="Wrap" Text="{Binding TotalCO2, Converter={StaticResource KgToTonnesConverter}}" FontSize="13.333" />