带转换器的C＃WPF绑定路径数据

Question

i have a problem converting a string to a icon. The icon Geometry is in a ResourceDictionary. The ValueConverter is not called (i tried to debug in the Convert Method of the Converter). Here is my code:

xaml:

<Window.Resources>
    <local:StatusToPathDataConverter x:Key="PathConverter"/>
</Window.Resources>
<Grid>
    <Path Width="20"
        Height="20"
        Stretch="Uniform"
        Fill="Black" 
        Data="{Binding Path=Status,
             UpdateSourceTrigger=PropertyChanged, 
             Converter={StaticResource PathConverter}}"/>
</Grid>

cs:

public partial class MainWindow :Window {
    public MainWindow() {
        InitializeComponent();
    }

    public string Status
    {
        get { return (string)GetValue(StatusProperty); }
        set { SetValue(StatusProperty, value); }
    }

    public static readonly DependencyProperty StatusProperty =
         DependencyProperty.Register("Status", typeof(string), typeof(MainWindow));


}
public class StatusToPathDataConverter :IValueConverter {
    private static ResourceDictionary iconDictionary;
    public ResourceDictionary IconDictionary
    {
        get
        {
            if(iconDictionary == null) {
                iconDictionary = new ResourceDictionary();
                iconDictionary.Source = new Uri("/WPFBindingTest;component/Resources/IconDictionary.xaml", UriKind.RelativeOrAbsolute);
            }
            return iconDictionary;
        }
    }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture) {
        var status = (string)value;
        if(statinStatus == null)
            return null;
        switch(status.ToLower()) {
            case "test":
                return IconDictionary["TestIcon"];
                // ...
        }
        return null;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) {
        throw new NotImplementedException();
    }
}

Answer 1

You're not binding to anything. You need to tell the Binding to go to the Window to find the Status property. The recommended way to do that is to use RelativeSource , as below:

<Path 
    Width="20"
    Height="20"
    Stretch="Uniform"
    Fill="Black" 
    Data="{Binding Path=Status,
         RelativeSource={RelativeSource AncestorType=Window},
         Converter={StaticResource PathConverter}}"
         />

As @Clemens notes, UpdateSourceTrigger=PropertyChanged doesn't make any sense on this binding and should not be there. That attribute tells the Binding when it should update the binding's source property. The source property is Window.Status , in this case.

However, the Path.Data property does not update the property it's bound to. A Path displays a Geometry ; it doesn't edit a Geometry . UpdateSourceTrigger exists for control properties that update viewmodel properties, like TextBox.Text . That's the most common use for UpdateSourceTrigger=PropertyChanged : By default TextBox.Text updates the source property when the TextBox loses focus, but sometimes you want it to update on each keystroke.

Answer 2

Set the DataContext of the window to itself for the binding to work and the Convert method of the converter to get called:

public MainWindow() {
    InitializeComponent();
    DataContext = this;
}

If the binding to the source property fails the converter will never be invoked.