Binding StringFormat

Question

I have a collection of textblocks that I'm going to be showing and I'm needing the text of each textblock to be displayed differently. I'm currently saving the format string in the tag property and I'm needing to display the text in this format. How do I bind the StringFormat section?

Something like the section below:

<TextBlock Tag="{Binding MyFormatString}" Text="{Binding MyProperty, StringFormat='{}{0:MyTag}'}" />

Answer 1

Since BindingBase.StringFormat is not a dependency property, I do not think that you can bind it. If the formatting string varies, I'm afraid you will have to resort to something like this

<TextBlock Text="{Binding MyFormattedProperty}" />

and do the formatting in your view model. Alternatively, you could use a MultiBinding and a converter (example code untested):

<TextBlock>
    <TextBlock.Text>
        <MultiBinding Converter="{StaticResource myStringFormatter}">
            <Binding Path="MyProperty" />
            <Binding Path="MyFormatString" />
        </MultiBinding>
    </TextBlock.Text>
</TextBlock>

public class StringFormatter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        return string.Format((string)values[1], values[0]);
    }
    ...
}

Answer 2

The String Formatting is a display setting and therefore should live close to the UI layer, you can either declare it in the Xaml or have formatted string properties on a ViewModel and perform the formatting in the Get of those properties and bind the TextBlock to it the ViewModel properties. It would source its data from the original datasource.