Question

我有三个TEXTBOX绑定到LABEL。当我在TEXTBOX中键入内容时，TextBox文本值设置为Label。 问题是我想在文本框为空白时将LABEL的Visiblity设置为COLLAPSED，反之亦然。如何在WPF中使用Visibility Convert来实现？

<。>在.XAML文件中：

<TextBox Name="txtEmail1" Grid.Column="1" Grid.Row="0" Text="Email" HorizontalAlignment="Stretch" Margin="2" VerticalAlignment="Stretch"/>
<TextBox Name="txtEmail2" Grid.Column="1" Grid.Row="0" Text="Email2" Visibility="Collapsed" Margin="2" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"/>
<TextBox Name="txtEmail3" Grid.Column="1" Grid.Row="0" Text="Email3" Visibility="Collapsed" Margin="2" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"/>

<Label Name="lblContactEmail1" Content="{Binding Path=Text, ElementName=txtEmail1, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Stretch" HorizontalAlignment="Stretch"/>
<Label Name="lblContactEmail2" Content="{Binding Path=Text, ElementName=txtEmail2, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Stretch" HorizontalAlignment="Stretch"/>
<Label Name="lblContactEmail3" Content="{Binding Path=Text, ElementName=txtEmail3, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Stretch" HorizontalAlignment="Stretch"/>

我试过：使用以下类StringToVisibilityConverter.cs

<UserControl xmlns:dxe="http://schemas.devexpress.com/winfx/2008/xaml/editors"  x:Class="XtremeProcurementWPF.UserControls.usContactForm"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:cv="clr-namespace:MyWPF"
             mc:Ignorable="d">
<UserControl.Resources>
        <cv:StringToVisibilityConverter x:Key="visibilityconverter" />
    </UserControl.Resources>
<Grid>
<TextBox Name="txtEmail1" Grid.Column="1" Grid.Row="0"  Text="Email" HorizontalAlignment="Stretch" Margin="2" VerticalAlignment="Stretch" />
    <Label Name="lblContactEmail1" Content="{Binding Path=Text, ElementName=txtEmail1, Mode=OneWay, UpdateSourceTrigger=PropertyChanged,Converter={StaticResource visibilityconverter}}" VerticalAlignment="Stretch" HorizontalAlignment="Stretch"/>
</Grid>
</UserControl>

问题：它将LABEL的文本显示为“可见”，而不是在文本框中输入的确切文本。

帮助感谢！谢谢！

Answer 1

创建自己的IValueConverter界面实现：

public class StringToVisibilityConverter: IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        var s = value as string;

        if (string.IsNullOrWhiteSpace(s))
            return Visibility.Collapsed;

        return Visibility.Visible;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

现在您资源中的某处注册了转换器：

<converters:StringToVisibilityConverter x:Key="StringToVisibilityConverter" />

最后，你在元素上使用转换器，如下所示：

<Label Name="lblContactEmail3" 
Visibility="{Binding Path=Text, ElementName=txtEmail3, Converter={StaticResource StringToVisibilityConverter}}" ... />

修改

以下是Label的完整代码：

<Label Name="lblContactEmail1" Content="{Binding Path=Text, ElementName=txtEmail1, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" Visibility="{Binding Path=Text, ElementName=txtEmail1, Converter={StaticResource visibilityconverter}}" VerticalAlignment="Stretch" HorizontalAlignment="Stretch"/>

Answer 2

你可以像这样使用DataTrigger：

   <StackPanel>
      <StackPanel.Resources>
         <Style TargetType="{x:Type Label}">
            <Style.Triggers>
               <DataTrigger Binding="{Binding ElementName=txtEmail1, Path=Text}" Value="">
                  <Setter Property="Visibility" Value="Collapsed"/>
               </DataTrigger>
            </Style.Triggers>
         </Style>
      </StackPanel.Resources>

      <TextBox Name="txtEmail1" Text="Email" />
      <Label Name="lblContactEmail1" Background="Yellow" Content="{Binding Path=Text, ElementName=txtEmail1}" />
   </StackPanel>

在此仅限XAML的解决方案中无需其他类。当然，你必须根据自己的需要（例如绑定）进行调整。我省略了不必要的属性。

如何设置绑定到Textbox的Label的可见性？

2 个答案: