条件XAML绑定(Conditional XAML

编程入门行业动态更新时间:2024-10-26 05:22:04

条件XAML绑定(Conditional XAML-Binding)

我想创建一个类似于Microsoft Outlook的窗口标题。

为此，我创建了以下绑定：

现在，我想知道如何使第二个绑定成为条件。例如当biSendAsHtml.IsChecked等于true显示HTML，否则显示纯文本 。

I'd like to create a window title similar to Microsoft Outlook's one.

For that, I've created the following binding:

Now I'd like to know how I can make the second binding conditional. Such as when biSendAsHtml.IsChecked equals true display HTML else display Plain Text.

最满意答案

我不确定你认为sa_ddam213的答案是否优雅，这只是可怕的。转发器，如RV1987建议，是正确的方法，但你可以更聪明。

创建一个转换器，它接受一个bool并将其转换为Converter定义中定义的选项。

public class BoolToObjectConverter : IValueConverter
{
    public object TrueValue { get; set; }
    public object FalseValue { get; set; }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return Convert.ToBoolean(value) ? TrueValue : FalseValue;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}
 
 定义转换器：  
<local:BoolToObjectConverter x:Key="SendAsHtmlBoolToTextConverter"
                             TrueValue="HTML"
                             FalseValue="Plain Text"/>
 
 并使用它：  
<MultiBinding StringFormat="{}{0} - Message ({1})}">
    <Binding ElementName="txtSubject" Path="Text" />
    <Binding ElementName="biSendAsHtml" Path="IsChecked"
             Converter="{StaticResource SendAsHtmlBoolToTextConverter}"/>
</MultiBinding>
 
 如果您愿意，甚至可以使TrueValue和FalseValue DependencyProperties支持Binding。 
I'm not sure how you think sa_ddam213's answer is elegant, it's just scary. The converter, like RV1987 suggested, is the correct approach, but you can be a lot smarter. 
Create a converter which takes a bool and converts it into options defined in the Converter definition. 
public class BoolToObjectConverter : IValueConverter
{
    public object TrueValue { get; set; }
    public object FalseValue { get; set; }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return Convert.ToBoolean(value) ? TrueValue : FalseValue;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}
 
Define the Converter: 
<local:BoolToObjectConverter x:Key="SendAsHtmlBoolToTextConverter"
                             TrueValue="HTML"
                             FalseValue="Plain Text"/>
 
And use it: 
<MultiBinding StringFormat="{}{0} - Message ({1})}">
    <Binding ElementName="txtSubject" Path="Text" />
    <Binding ElementName="biSendAsHtml" Path="IsChecked"
             Converter="{StaticResource SendAsHtmlBoolToTextConverter}"/>
</MultiBinding>
 
If you want you could even make TrueValue and FalseValue DependencyProperties to support Binding.