WPF MultiBinding - UnsetValue 问题

Question

我有一个文本块。当其文本绑定为：

<Binding Path="Applicant2.Surname"/>

它工作正常，但是我想包含名字，因此将绑定更改为：

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

这将显示 {DependencyProperty.UnsetValue} {DependencyProperty.UnsetValue} 直到第一次设置该值。

我怎样才能阻止这个？为什么我在第一个简单绑定时没有遇到问题？

Answer 1

对于多重绑定，您需要添加一个后备值，如果它只是空白，那么您可以简单地执行以下操作：

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

Answer 2

对于多重绑定，我使用了下面的代码并为我工作：

<MultiBinding Converter="{StaticResource ValueToAngle}" StringFormat="{}{0} {1}">
                        <MultiBinding.Bindings>
                            <Binding RelativeSource="{RelativeSource Mode=FindAncestor,AncestorType={x:Type UserControl}}" Path="TotalSkidCount"/>
                            <Binding RelativeSource="{RelativeSource Mode=FindAncestor,AncestorType={x:Type UserControl}}" Path="ActualCount"/>
                        </MultiBinding.Bindings>
                    </MultiBinding>

下面是它的属性：

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

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