WPF：ValueConverter (IValueConverter) 不起作用

Question

我有一个 Window class，其中我有几个 TextBlock 元素应该接收 Background 颜色 Binding 属性。第一个 "Converter binding" 工作正常并且完成了预期的一切。今天我尝试用另一个 Converter 实现另一个 "Converter binding"，但它不起作用：

（我省略了 ConvertBack 方法，因为它们在这里不是必需的）：

namespace InsightTool.Gui.Helper {
    [ValueConversion(typeof(double), typeof(Brush))]
    public class AverageExecutionTimeToColorConverter : IValueConverter {
        public object Convert (object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) {
            double val;
            double.TryParse(value.ToString(), out val);

            if (val >= 10000) {
                return Brushes.Red;
            } else if (val >= 5000) {
                return Brushes.Orange;
            } else {
                return Brushes.Green;
            }
        }
    }

    [ValueConversion(typeof(int), typeof(Brush))]
    public class ThreadsAvailableCountToColorConverter : IValueConverter {
        public object Convert (object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) {
            int val;
            int.TryParse(value.ToString(), out val);

            if (val < 100) {
                return Brushes.Red;
            } else if (val < 200) {
                return Brushes.Orange;
            } else if (val < 500) {
                return Brushes.Yellow;
            } else {
                return Brushes.Green;
            }
        }
    }
}

在 Window class 中，我使用了以下两个转换：

<Window ...
    x:Name="Main"
    xmlns:Base="clr-namespace:InsightTool.Gui.Helper">
    <Window.Resources>
        <Base:ThreadsAvailableCountToColorConverter x:Key="ThreadsAvailableCntConverter"/>
        <Base:AverageExecutionTimeToColorConverter x:Key="AvgExecutionTimeConverter"/>     
    </Window.Resources>

    <!-- This one works fine-->
    <TextBlock Width="10" Height="10" VerticalAlignment="Center" Background="{Binding ExecutionTimeAverage, Converter={StaticResource AvgExecutionTimeConverter}, ElementName=UCExecutionTimes}"/>

    <!-- This one does not work-->
    <TextBlock Width="10" Height="10" VerticalAlignment="Center" Background="{Binding ThreadsAvailableCount, Converter={StaticResource ThreadsAvailableCntConverter}, ElementName=Main}"/>
</Window>

DependencyProperties 的声明：

public partial class UserControlExecutionTimes : UserControl {
    public static readonly DependencyProperty ExecutionTimeAverageProperty =
             DependencyProperty.Register("ExecutionTimeAverage", typeof(double), typeof(MainWindow), new FrameworkPropertyMetadata(double));

    public double ExecutionTimeAverage {
        get { return (double)GetValue(ExecutionTimeAverageProperty); }
        set { SetValue(ExecutionTimeAverageProperty, value); }
    }
}


public partial class MainWindow : Window {
    public static readonly DependencyProperty ThreadsAvailableCountProperty = DependencyProperty.Register("ThreadsAvailableCount", typeof(int),
         typeof(MainWindow), new FrameworkPropertyMetadata(int));

    public int ThreadsAvailableCount {
        get { return (int)GetValue(ThreadsAvailableCountProperty); }
        set { SetValue(ThreadsAvailableCountProperty, value); }
    }
}

两个 DependencyProperties 都设置正确并且它们的值显示在 GUI 中。我在这里想念什么？

编辑：

我还测试了以下内容：

<Window>
    <!-- This one works fine-->
    <TextBlock Width="10" Height="10" VerticalAlignment="Center" Background="{Binding ThreadsAvailableCount, Converter={StaticResource AvgExecutionTimeConverter}, ElementName=Main}"/>

    <!-- This one does not work-->
    <TextBlock Width="10" Height="10" VerticalAlignment="Center" Background="{Binding ThreadsAvailableCount, Converter={StaticResource ThreadsAvailableCntConverter}, ElementName=Main}"/>
</Window>

似乎Binding消耗"new"转换器的return值有问题，但我不知道为什么。

EDIT2

我用 Snoop 检查绑定，结果如下：

工作转换器绑定的 background 属性如下所示：

但是不工作的转换器绑定的 background 属性看起来是这样的：

ThreadsAvailableCount 设置正确的另一个证明（绑定到 Textblock）：

显示ThreadsAvailableCountToColorConverter的return值越来越像错误了。这是因为在 Debug 模式下，它会在 ThreadsAvailableCountToColorConverter 的 Convert 方法中的断点处停止。它甚至在 Convert 方法中成功到达 return。

Answer 1

我认为可能存在多个问题，请查看 'output window' 以了解绑定表达式错误。 1) 确保文本框呈现在不同的区域，而不是重叠。 2）使用相对路径获取控件，在绑定表达式

中使用属性

你的转换器看起来不错。

以下是我的xaml

<Window x:Class="WhosebugBinding.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:WhosebugBinding="clr-namespace:WhosebugBinding"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <WhosebugBinding:ThreadsAvailableCountToColorConverter x:Key="ThreadsAvailableCntConverter"/>
        <WhosebugBinding:AverageExecutionTimeToColorConverter x:Key="AvgExecutionTimeConverter"/>
    </Window.Resources>
    <Grid>
        <!--<DatePicker 
        x:Name="newtally" 
        Text="{Binding CustomerLastTally,Mode=TwoWay}"  
        Margin="0 0 0 0" 
        />-->
        <!-- This one works fine-->
        <Grid.RowDefinitions>
            <RowDefinition></RowDefinition>
            <RowDefinition></RowDefinition>
            <RowDefinition></RowDefinition>
        </Grid.RowDefinitions>
        <TextBlock Grid.Row="0" Grid.Column="0" Width="30" Height="30" Text="Break"/>
        <TextBlock Grid.Row="1" Grid.Column="0"  Width="30" Height="30" VerticalAlignment="Center"  Text="Break" Background="{Binding ExecutionTimeAverage, Converter={StaticResource AvgExecutionTimeConverter}, RelativeSource={RelativeSource AncestorType={x:Type Window}}}"/>

        <!-- This one does not work-->
        <TextBlock Grid.Row="2" Grid.Column="0"  Width="30" Height="30" VerticalAlignment="Center" Text="Break" Background ="{Binding ThreadsAvailableCount, Converter={StaticResource ThreadsAvailableCntConverter}, RelativeSource={RelativeSource AncestorType={x:Type Window}}}"/>
    </Grid>

</Window>

以下是我背后的代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WhosebugBinding
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        // Dependency Property
        public static readonly DependencyProperty ExecutionTimeAverageProperty =
             DependencyProperty.Register("ExecutionTimeAverage", typeof(DateTime),
             typeof(MainWindow), new FrameworkPropertyMetadata(DateTime.Now));

        // .NET Property wrapper
        public DateTime ExecutionTimeAverage
        {
            get { return (DateTime)GetValue(ExecutionTimeAverageProperty); }
            set { SetValue(ExecutionTimeAverageProperty, value); }
        }

        // Dependency Property
        public static readonly DependencyProperty ThreadsAvailableCountProperty =
             DependencyProperty.Register("ThreadsAvailableCount", typeof(int),
             typeof(MainWindow), new FrameworkPropertyMetadata(40));

        // .NET Property wrapper
        public int ThreadsAvailableCount
        {
            get { return (int)GetValue(ThreadsAvailableCountProperty); }
            set { SetValue(ThreadsAvailableCountProperty, value); }
        }
    }
}

以下是我的转换器

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Data;
using System.Windows.Media;

namespace WhosebugBinding
{

    [ValueConversion(typeof(double), typeof(Brush))]
    public class AverageExecutionTimeToColorConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            double val;
            double.TryParse(value.ToString(), out val);

            if (val >= 10000)
            {
                return Brushes.Red;
            }
            else if (val >= 5000)
            {
                return Brushes.Orange;
            }
            else
            {
                return Brushes.Green;
            }
        }

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

    [ValueConversion(typeof(int), typeof(Brush))]
    public class ThreadsAvailableCountToColorConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            int val;
            int.TryParse(value.ToString(), out val);

            if (val < 100)
            {
                return Brushes.Red;
            }
            else if (val < 200)
            {
                return Brushes.Orange;
            }
            else if (val < 500)
            {
                return Brushes.Yellow;
            }
            else
            {
                return Brushes.Green;
            }
        }

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

Answer 2

啊！终于解决了这个问题。我有同样的问题。使用 TextBlock，使用 IValueConverter 将 转换为 Brush.

绑定有效，没有错误或输出。该值进入 IValueConverter 代码，我可以直接调试到 return 语句，然后......什么都没有！

你做的一切都是对的，但是你自动导入了错误的Brushes。我一直用 WPF 做这件事。

替换 using 语句：

using System.Drawing

与：

using System.Windows.Media

WPF 使用 System.Windows.Media.Brushes，但非常很容易导入几乎相同的 System.Drawing.Brushes 而没有注意到。一切看起来都很好，直到 WPF 掌握它并且不能实际使用它。但是它失败了 'gracefully' 回到默认颜色。

WPF：ValueConverter (IValueConverter) 不起作用

WPF: ValueConverter (IValueConverter) does not work

c#

wpf

xaml

binding

valueconverter