Binding StringFormat to a binding

Question

Can I bind StringFormat inside a Binding to another Binding?

Text="{Binding DeficitDollars, StringFormat=\{0:E6\}}"

Text="{Binding GNP, StringFormat={Binding LocalCurrencyFormat}}"

Similar to this: http://stackoverflow.com/a/15309844/1136211 — Clemens, Jan 30 '16 at 13:22

score 1 · Accepted Answer · answered Jan 30 '16 at 13:09

You can't use a Binding for StringFormat. As the exception tells you if you try it:

A 'Binding' can only be set on a DependencyProperty of a DependencyObject

StringFormat is not a DependencyProperty and Binding is not a DependencyObject.

You can do these two things though.

Setting it to a resource.

You can define your different string formats in App.xaml in the Resources so they'll be reachable in the whole application:

<system:String x:Key="LocalCurrencyFormat">{0:C}</system:String>

system is xmlns:system="clr-namespace:System;assembly=mscorlib"

And then you can do:

<TextBlock Text="{Binding MyDouble, StringFormat={StaticResource LocalCurrencyFormat}}" />

Setting it to a static property of a class.

You can have a class with all your different string formats:

public static class StringFormats
{
    public static string LocalCurrencyFormat
    {
        get { return "{0:C}"; }
    }
}

And use it in the Binding the following way:

<TextBlock Text="{Binding MyDouble, StringFormat={x:Static local:StringFormats.LocalCurrencyFormat}}" />

These are good patterns. I was really looking for something more dynamic, where I could define the Formats in a Template and then pass info from my End-User XAML page into the template and there would be some logic. I Think I can put that logic instead into a Converter in the Template. Right now, App.xaml is sufficient, but I certainly see that becoming a maintenance nightmare as it becomes a clearinghouse for thousands of build-specific configuration parameters. I'd rather tie to and have more dynamic capabilities of - the {Binding}- to a Class or Template-Class or User-Control property. — Andyz Smith, Jan 31 '16 at 15:03

score 0 · Answer 2 · answered Jan 30 '16 at 19:33

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:sys="clr-namespace:System;assembly=mscorlib"
        Width="500" Height="500">

    <Window.Resources>
        <sys:String x:Key="LocalCurrencyFormat">Total: {0:C}</sys:String>
    </Window.Resources>
    <StackPanel>
        <TextBlock Text="{Binding DeficitDollars, StringFormat=\{0:E6\}}"></TextBlock>
        <TextBlock Text="{Binding Path=GNP, StringFormat={StaticResource LocalCurrencyFormat}}" />
    </StackPanel>
</Window>

I suppose you can do this, but other answers are better because they define these constants externally. — Andyz Smith, Jan 31 '16 at 14:59

Binding StringFormat to a binding

2 Answers2