多语言WPF应用程序：不能与组合框一起使用

Question

I have created a multilingual WPF application using Andre's answer from here . I'm binding text like this

<TextBlock Text="{DynamicResource Create}"/>

and can switch from english to french at runtime - nice! However, this does not work with ItemsSource. For example, I have a ComboBox that should display all available languages:

<ComboBox ItemsSource="{Binding AllLanguages, Source={StaticResource Locator}}">
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{DynamicResource LanguageId}"/>
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>

Set up like this, the combobox displays no text. If I set the textblock's text inside to Text={LanguageId} , I see the LanguageIds 'eng', 'fr' etc., so the binding works.

When using a converter:

<TextBlock Text="{Binding LanguageId, Converter={StaticResource DynamicResourceConverter}"/>

languages are displayed as "English" and "French". When I switch the language, however, the converter is not called again and the language names are not updated - so that is no real workaround.

I'd be very thankful for a tip on the cause and how to fix this.

Answer 1

I'll explain first why a few things are not working.

    ....
    <DataTemplate>
        <TextBlock Text="{DynamicResource LanguageId}"/>
    </DataTemplate>
    ....

This is a short hand for Text="{DynamicResource ResourceKey='LanguageId'}" which is a static string literal and does not involve any binding.

It would be great if the following was available, but unfortunetly is NOT POSSIBLE because the target for the binding is not a DependancyProperty .

    ....
    <DataTemplate>
        <TextBlock Text="{DynamicResource ResourceKey={Binding LanguageId}}"/>
    </DataTemplate>
    ....

You are close with your workaround. My suggestion would be to try the following:-

    ....
    <DataTemplate>
        <TextBlock>
            <TextBlock.Text>
                <MultiBinding Converter="{StaticResource DynamicResourceConverter}">
                    <Binding Path="LanguageId"/>
                    <Binding Path="SomeOtherPropertyThatChangesWhenLanguageIsSwitched" Source="{StaticResource Locator}"/>
                </MultiBinding>
            </TextBlock.Text>
        </TextBlock>
    </DataTemplate>
    ....

You will need to expand the DynamicResourceConverter to now implement also IMultiValueConverter . In a MultiBinding scenario, if either bound expression changes then the converter is called again. You would write the Converter such that it only operates on values[0] of the supplied object array as the second value is not needed and only provided a trigger for the converter to be called again.

    public class DynamicResourceConverter: IValueConverter, IMultiValueConverter
    {
        ....
        // original converter implementation for IValueConverter
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            ....
        }

        // newly added converter implementation for IMultiValueConverter
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            //call the original converter method with one value (assuming you've checked the array has at least one item!!
            return Convert(values[0], targetType, parameter, culture)
        }

        ....
    }