String manipulation in XAML property databinding for Hyperlinks

Question

Is there an easy way to transform or format a string as part of WPF data binding?

Suppose I want to create a WPF Hyperlink element based on a string tag.

<Hyperlink NavigateUri="{Binding Tag}">
    <Run Text="{Binding Tag}" />
</Hyperlink>

But I need to transform the Tag first for the NavigateUri property to make it a true hyperlink or PackUri.

For instance, if my tag were "folksonomy" I'd want to create a string like: http://www.example.com/tags/tagview?tag=folksonomy

What's the best way to achieve this? Is there a string manipulation function in XAML? Do I have to write a converter? Do a have to build a whole separate ViewModel class just to do a little string formatting?

UPDATE: There appears to be something strange going on with the Hyperlink element. I can get the StringFormat syntax suggested in the answers to work for an ordinary TextBlock, but not for a Hyperlink. I've tried both the NavigateUri and ToolTip properties, and neither seems to respect the StringFormat settings.

So apparently a custom converter or ViewModel property will be required.

Answer 1

You can use the string formatting capabilities of bindings:

<Hyperlink NavigateUri="{Binding Tag, StringFormat=http://www.example.com/tags/tagview?tag={0}}"&gt;
    <Run Text="{Binding Tag}" />
</Hyperlink>

HTH,
Kent

Answer 2

Like Kent said you can use string formatting assuming you are on .NET 3.5 SP1 (string formatting was added as part of SP1). Good Samples here: http://blogs.msdn.com/b/llobo/archive/2008/05/19/wpf-3-5-sp1-feature-stringformat.aspx

If you aren't on .NET 3.5 SP1 or the string format approach becomes too messy you would want to us an IValueConverter http://msdn.microsoft.com/en-us/library/system.windows.data.ivalueconverter.aspx

Answer 3

For anyone else stumbling across this thread seeking a solution, I found Foovanadil's suggested IValueConverter worked well for me.

<TextBlock> 
    <Hyperlink Name="lnkGoogle" NavigateUri="{Binding Path=Alert.Query,Converter={View:UriConverter},ConverterParameter=google}" RequestNavigate="Hyperlink_RequestNavigate">
        Find news on Google
    </Hyperlink>
</TextBlock>

With the converter class in my codebehind:

public class UriConverter : MarkupExtension, IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            string address = string.Empty;
            switch ((string)parameter)
            {
                case "google":
                    address = "http://www.google.co.uk/news?q=" + value;
                    break;                    
            }

            Uri path = new Uri(@address);
            return path;
        }

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

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