<Binding Path="Applicant2.Surname"/>

<MultiBinding StringFormat="{}{0} {1}">
    <Binding Path="Applicant2.Forenames"/>
    <Binding Path="Applicant2.Surname"/>
</MultiBinding>

<MultiBinding StringFormat="{}{0} {1}">
    <Binding Path="Applicant2.Forenames" FallbackValue=""/>
    <Binding Path="Applicant2.Surname" FallbackValue=""/>
</MultiBinding>

public int TotalSkidCount { get { return (int)GetValue(TotalSkidCountProperty); } set { SetValue(TotalSkidCountProperty, value); } }
    public static readonly DependencyProperty TotalSkidCountProperty = DependencyProperty.Register("TotalSkidCount", typeof(int), typeof(CirculerProgressBarControl));