Is it possible to define converter for binding inline (without resource)?

Question

Is it possible to define type converter for binding inline (without resource)?

Something like this:

   <Button Visibility="{Binding ElementName=checkBox, Path=IsChecked, Converter={new BooleanToVisibilityConverter}" />

Answer 1

You can create and expose your converter through a custom MarkupExtension which will give you the inline declaration you're looking for:

public class BooleanToVisibilityConverterExtension : MarkupExtension, IValueConverter
{
  private BooleanToVisibilityConverter converter;

  public BooleanToVisibilityCoverterExtension() : base()
  {
    this.converter = new BooleanToVisibilityConverter();
  }

  public override object ProvideValue(IServiceProvider serviceProvider)
  {
    return this;
  }

  public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
  {
    return this.converter.Convert(value, targetType, parameter, culture);
  }

  public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
  {
    return this.converter.ConvertBack(value, targetType, parameter, culture);
  }
}

Now you can use the MarkupExtension inline to create a new converter:

<Button Visibility="{Binding Converter={local:BooleanToVisibilityConverter} ...}" .. />

Answer 2

It's not possible using binding syntax. But it is possible using element syntax:

 <Button.Visibility>
    <Binding ElementName="checkBox" Path=IsChecked>
        <Binding.Converter>
            <BooleanToVisibilityConverter />
        </Binding.Converter>
    </Binding>
 </Button.Visibility>

But why would you want to do this? It would mean every binding instance will create a new converter. That's not efficient from a memory point of view.

Answer 3

You could do something like this. This should work.

Pseudocode :

public static class ConverterHost 
{ 
    public static readonly MyCoolConverter converter = new MyCoolConverter (); 
}

and in the XAML, somethign like this:

{Binding Converter={x:Static conv:ConverterHost.converter }}

Hope this helps.

Regards.

Answer 4

No, you have to define the converter as a resource somewhere (window, usercontrol, etc.) before you can use it in a binding.