String format using UWP and x:Bind

Use a StringFormatConverter (check if you maybe use some library, which already includes it, e.g. the UWP Toolkit (thanks, @maxp) or the older Cimbalino Toolkit):

public class StringFormatConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, string language)
    {
        if (value == null)
            return null;

        if (parameter == null)
            return value;

        return string.Format((string)parameter, value);
    }

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

add it to your page resource

<Page.Resources>
    <converters:StringFormatConverter x:Key="StringFormatConverter" />
</Page.Resources>

and use it like this

<TextBlock Text="{x:Bind Text, Converter={StaticResource StringFormatConverter}, ConverterParameter='{}{0:dd/MM/yyy HH\\\\:mm (ddd)}'}" />

you can use

{x:Bind ViewModel.DateTimeProperty.ToString("....")}

Function binding is much better approach than classic Converter:

 <TextBlock Text="{x:Bind DateTimeToString(MyDateTime,'dd/MM/yyy HH\\\\:mm (ddd)')}" />

Code behind (it could be placed in separate class):

//"Converter"
public string DateTimeToString(DateTime dateTime, string format) => dateTime.ToString(format);

public DateTime MyDateTime { get; set; } = DateTime.Now;

Why is it better than classic converter?

• Shorter -> no boil plait code
• Strongly typed -> Detects exceptions in build time.