Sorry. I forgot that the default styles for the RibbonTabItem will strip out the mnemonics of the Header string because that is how Office behaves. It uses those mnemonics as the default keytip. It looks like you'll have to modify the string, change the default styles or just use a custom IValueConverter that will escape the mnemonics. For the latter you might even be able to use a utility method we have.

e.g.

    public class EscapeMnemonicsConverter : IValueConverter
    {
        object IValueConverter.Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            var strValue = value as string;

            if (strValue != null)
                return Infragistics.Windows.Utilities.StripMnemonics("_" + strValue, true);

            return Binding.DoNothing;
        }

        object IValueConverter.ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return Binding.DoNothing;
        }
    }

So then you'd define an instance of this converter in the resources and use that in your binding.

e.g.

<igWpf:XamRibbon>
    <igWpf:XamRibbon.Resources>
        <local:EscapeMnemonicsConverter x:Key="escapeMnemonics" xmlns:local="clr-namespace:WpfApplication3" />
    </igWpf:XamRibbon.Resources>
    <igWpf:RibbonTabItem Header="{Binding ItemName, Converter={StaticResource escapeMnemonics}}" />
</igWpf:XamRibbon>

Thanks for the fast reply.

The option with the escape char is not acceptable in this case, since the strings displayed are loaded from an existing costumer DB with several 100K long lists (and manipulating the header text itself, before displaying it, is a workaround I simply want to avoid...).

I tried the DataTemplate option with two settings however neither worked (in both the _ was not displayed correctly):

Option one:

          <igRibbon:RibbonTabItem Header="{Binding ItemName}">

                <igRibbon:RibbonTabItem.HeaderTemplate>

                    <DataTemplate>

                        <TextBlock Text="{Binding}"/>

                    </DataTemplate>

                </igRibbon:RibbonTabItem.HeaderTemplate>

Option Two:

           <igRibbon:RibbonTabItem Header="{Binding ItemName}">

                <igRibbon:RibbonTabItem.HeaderTemplate>

                    <DataTemplate>

                        <TextBlock>

                            <ContentPresenter Content="{Binding}"  RecognizesAccessKey="False"/>

                        </TextBlock>

                    </DataTemplate>

                </igRibbon:RibbonTabItem.HeaderTemplate>

Did I do a mistake perhaps?

Regards BB