将值传递给IValueConverter

本文关键字：IValueConverter 值传 | 更新日期: 2023-09-27 18:16:50

我有一个ListView，它有一个Grid，有两列和多行。每行在每列中都有一个TextBlock，每个Text属性绑定到ListView的ItemSource中的一个值。我需要根据第一个TextBlock的值对第二个TextBlock中的文本进行一些转换。如何将第一个文本框的值转换为转换器?

到目前为止我写的是:

XAML: 

<UserControl.Resources>
    <local:ValueStringConverter x:Key="valueStringConverter" />
</UserControl.Resources>
<ListView Name="theListView" ItemsSource="{Binding ItemCollection}" SelectedItem="{Binding SelectedItem}" ScrollViewer.HorizontalScrollBarVisibility="Disabled" Grid.Row="1" >
    <ListView.ItemTemplate>
        <DataTemplate>
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition Height="Auto" />
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="Auto" />
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>
                <TextBlock Text="{Binding Path=Key}" Grid.Column="0" Margin="0,0,10,0" />
                <TextBlock Text="{Binding Path=Value, Converter={StaticResource valueStringConverter}}" TextWrapping="Wrap" Grid.Column="1" />
            </Grid>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

ValueStringConverter代码:

public class ValueStringConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        string name = (string)value;
        name = name.Replace("$$", " ");
        name = name.Replace("*", ", ");
        name = name.Replace("##", ", ");
        return value;
    }
    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

将值传递给IValueConverter

不能将多个值传递给"常规"值转换器。您可以使用multivalueconverter并将绑定定义为MultiBinding。

或者你可以创建一个IValueConverter，它接受DataContext中的整个对象，将对象强制转换为它的类型，接受Value和Key并返回你需要的字符串。

在第二个文本块中，将绑定定义为

<TextBlock Text="{Binding Converter={StaticResource valueStringConverter}"/>

和你的转换器为:

public class ValueStringConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        MyDataContextObjectType obj= (MyDataContextObjectType)value;
        var name= obj.Name;
        var key = obj.Key;
        //here you have both Name and Key, build your string and return it
        //if you don't know the type of object in the DataContext, you could get the Key and Name with reflection
        name = name.Replace("$$", " ");
        name = name.Replace("*", ", ");
        name = name.Replace("##", ", ");
        return value;
    }
    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

尝试多重绑定。你需要一个IMultiValueConverter:

public class MultiValueConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        var key   = (string)values[0];
        var value = (string)values[1];
        // replace with appropriate logic
        var result = key + ": " + value;
        return result;
    }
    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

和稍微修改过的XAML:

<TextBlock Text="{Binding Path=Key}" Grid.Column="0" Margin="0,0,10,0" />
<TextBlock TextWrapping="Wrap" Grid.Column="1">
    <TextBlock.Text>
        <MultiBinding Converter={StaticResource valueStringConverter}>
            <Binding Path="Key" />
            <Binding Path="Value" />
        </MultiBinding>
    </TextBlock.Text>
</TextBlock>

绑定到实例，而不是属性(本例中为value)。然后您将可以访问转换器中的Key和Value。

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