Multibinding生成“无法设置MultiBinding，因为必须指定MultiValueConverter”

Question

我有一个带绑定的按钮，工作正常，见下文：

<Button x:Name="licenceFilterSet" Content="Search" Command="{Binding searchCommand}" CommandParameter="{Binding Path=Text, ElementName=licenseTextBox}" />

现在我意识到我需要另一条信息，所以我也需要发送一个check-box的值。我修改了这样的VM：

<Button x:Name="licenceFilterSet" Content="Search" Command="{Binding licenseSearchCommand}">
    <Button.CommandParameter>
        <MultiBinding Converter="{StaticResource searchFilterConverter}">
            <Binding Path="Text" ElementName="licenseTextBox" />
            <Binding Path="IsEnabled" ElementName="regularExpressionCheckBox" />
        </MultiBinding>
    </Button.CommandParameter>
</Button>

下面是我的多转换器：

/// <summary>
/// Converter Used for combining license search textbox and checkbox
/// </summary>
public class SearchFilterConverter : IMultiValueConverter
{
    public object Convert(object[] values)
    {
        return new Tuple<String, bool>((String)values[0], (bool)values[1]);
    }
}

我究竟做错了什么。我收到以下错误，（指向我在XAML中的MultiBinding标记）：

Cannot set MultiBinding because MultiValueConverter must be specified.

Answer 1

你必须实现IMultiConverter

public class SearchFilterConverter : IMultiValueConverter
{
 public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
 {
    return new Tuple<String, bool>((String)values[0], (bool)values[1]);;
 }
 public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

然后在xaml中创建资源

 <Converter:SearchFilterConverter x:Key="searchFilterConverter" />

那它应该工作

<Button x:Name="licenceFilterSet" Content="Search" Command="{Binding licenseSearchCommand}">
<Button.CommandParameter>
    <MultiBinding Converter="{StaticResource searchFilterConverter}">
        <Binding Path="Text" ElementName="licenseTextBox" />
        <Binding Path="IsEnabled" ElementName="regularExpressionCheckBox" />
    </MultiBinding>
</Button.CommandParameter>
</Button>

Answer 2

这不是IMultiValueConverter接口的正确实现。

正确的是：

public class SearchFilterConverter : IMultiValueConverter
{
   public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
   {
      ....
   }

   public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
   {
   }
}

参考here。