如何设置绑定到文本框的标签的可见性

本文关键字：文本 标签 可见性 绑定 何设置 设置 | 更新日期: 2023-09-27 18:19:50

我有三个绑定到LABEL的TEXTBOX。当我在TEXTBOX中键入内容时，TEXTBOX文本值将设置为Label问题是当文本框为空时，我想将LABEL的Visiblity设置为COLLAPSED，反之亦然。如何在WPF中使用可见性转换？

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"/>

我尝试过：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

感谢帮助！谢谢

如何设置绑定到文本框的标签的可见性

创建自己的IValueConverter接口实现：

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，在您的资源中的某个位置注册您的转换器：

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

最后，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}}" ... />

编辑：

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"/>

您可以使用这样的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>

在这个仅XAML的解决方案中不需要其他类。当然，您必须根据自己的需要进行调整（例如绑定）。我省略了不必要的属性。

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