WPF：通过字符串内容绑定可见性
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WPF: Binding Visibility by string contents
提问by Jonathan Allen
Ok, so here is my XAML:
好的，这是我的 XAML：
<TextBlock Text="{Binding Path=InstanceName}"></TextBlock>
If InstanceNameis null or an empty string, I want Visibility="Collapsed". Otherwise I want Visibility="Visible". How would I do that?
如果InstanceName为 null 或空字符串，我想要Visibility="Collapsed". 否则我要Visibility="Visible"。我该怎么做？
回答by Markus Hütter
You could use a ValueConverter:
您可以使用 ValueConverter：
<TextBlock
Visibility="{Binding InstanceName, Converter={local:StringNullOrEmptyToVisibilityConverter}}"
Text="{Binding InstanceName}"/>
with the following codebehind:
带有以下代码隐藏：
public class StringNullOrEmptyToVisibilityConverter : System.Windows.Markup.MarkupExtension, IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return string.IsNullOrEmpty(value as string)
? Visibility.Collapsed : Visibility.Visible;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return null;
}
public override object ProvideValue(IServiceProvider serviceProvider)
{
return this;
}
}
回答by Matthias
If you are inside a (Data-)Template you can use Triggersfor that.
如果您在 (Data-)Template 中，您可以使用触发器。
Otherwise, the MVVM-Patternor a ValueConverterwill help you.
否则，MVVM-Pattern或ValueConverter将帮助您。
回答by Peter Lillevold
By putting an extra property in your viewmodel that you can bind the Visibility attribute to:
通过在您的视图模型中放置一个额外的属性，您可以将 Visibility 属性绑定到：
public class ViewModel
{
public string InstanceName {...}
public Visibility InstanceVisibility
{
get
{
return String.IsNullOrEmpty(InstanceName) ? Visibility.Collapsed : Visibility.Visible;
}
}
回答by Kishore Kumar
<TextBlock Text="{Binding Path=InstanceName},FallbackValue={x:Null}"></TextBlock>
Then add a DataTrigger to check the value is null and change visibility using Setter. This is the simple method which iam using.
然后添加一个 DataTrigger 来检查值是否为 null 并使用 Setter 更改可见性。这是我使用的简单方法。
回答by Jonathan Allen
Ok, so this is close with PyBinding:
好的，这与 PyBinding 很接近：
<TextBlock Text="{Binding Path=InstanceName}" Visibility="{p:PyBinding BooleanToVisibility(IsNotNull($[.InstanceName]))}" ></TextBlock>
I need to replace IsNotNull with something that means IsNotNullOrEmpty, but I'm getting closer.
我需要用意味着 IsNotNullOrEmpty 的东西替换 IsNotNull，但我越来越接近了。
