Problem with StringFormat

Question

I'm trying to use the StringFormat in XAML to populate the Header text on a TabItem. The code I am using is:

<TabControl.ItemContainerStyle>
    <Style TargetType="{x:Type TabItem}" BasedOn="{StaticResource TabItemStyle}">
        <Setter Property="Header" Value="{Binding MyValue, StringFormat='My Value is {0}'}" />
        <EventSetter Event="FrameworkElement.Loaded" Handler="OnTabItemLoaded" />
        <EventSetter Event="FrameworkElement.Unloaded" Handler="OnTabItemUnloaded" />
    </Style>
</TabControl.ItemContainerStyle>

The problem is my header is only showing the value of MyValue in the Header and not the formatted text.

you should consider setting the HeaderStringFormat answer as the correct one. It's a 15 second fix rather than a 15 minute one. — Jamie
– Jamie, Commented Jul 21, 2023 at 2:10

Bob Vale · Accepted Answer · 2011-09-14 11:37:50Z

5

Because the Header property is not a string property.

You need to use a headertemplate containing a TextBlock which you can bind the Text property using your stringformat

<TabControl.ItemContainerStyle> 
    <Style TargetType="{x:Type TabItem}" BasedOn="{StaticResource TabItemStyle}"> 
        <Setter Property="HeaderTemplate">
          <Setter.Value>
            <DataTemplate>
              <TextBlock Text="{Binding MyValue, StringFormat='My Value is {0}'}" /> 
            </DataTemplate>
          </Setter.Value>
        </Setter>
        <EventSetter Event="FrameworkElement.Loaded" Handler="OnTabItemLoaded" /> 
        <EventSetter Event="FrameworkElement.Unloaded" Handler="OnTabItemUnloaded" /> 
    </Style> 
</TabControl.ItemContainerStyle>

edited Sep 14, 2011 at 11:37

answered Sep 14, 2011 at 0:42

Bob Vale

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2 Comments

lumberjack4 Over a year ago

I had to change the ControlTemplate to a DataTemplate, but that gave me exactly what I was looking for.

Eduardo Hernández Over a year ago

I think nowadays you can simply use HeaderStringFormat, see my answer below.

Eduardo Hernández · Accepted Answer · 2019-09-11 08:50:27Z

2

The simplest solution is to use the HeaderStringFormat property:

<Setter Property="Header" Value="{Binding MyValue}" />
<Setter Property="HeaderStringFormat" Value="My Value is {0}" />

WPF seems to follow this pattern whenever you can assign a string to a generic content property, another example would be ContentControl.ContentStringFormat.

answered Sep 11, 2019 at 8:50

Eduardo Hernández

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