WPF: ValueConverter (IValueConverter)不工作

Question

我有一个Window类，其中有几个TextBlock元素，它们应该通过Binding属性值接收Background颜色。第一个“转换器绑定”工作良好，并完成一切期望。今天，我尝试用另一个用于它的Converter实现另一个“转换器绑定”，但它不起作用：

(我省略了ConvertBack方法，因为它们在这里是不必要的)：

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类中，我使用了两个转换，如下所示：

<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的设置都是正确的，它们的值都显示在GUI中。我在这里错过了什么？

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使用“新”转换器的返回值存在问题，但我不知道原因。

EDIT2

我使用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，非工作转换器绑定的background属性如下所示：

​

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

​

显示ThreadsAvailableCountToColorConverter的返回值似乎越来越多地是一个错误。这是因为在调试模式下，它停止在Convert方法的ThreadsAvailableCountToColorConverter中的一个断点。它甚至在return方法中成功地达到Convert方法。

Answer 1

阿!终于解决了这个问题。我也有同样的问题。使用TextBlock，使用IValueConverter转换为Brush。

绑定工作正常，没有错误或输出。值进入IValueConverter代码，我可以直接调试到返回语句.没什么!

您做的一切都是正确的，但是您自动导入了错误的Brushes。我一直和WPF一起做。

替换using语句：

using System.Drawing

通过以下方式：

using System.Windows.Media

WPF使用System.Windows.Media.Brushes，但是很容易导入几乎相同的System.Drawing.Brushes而不需要注意。这一切看起来都很好，直到WPF掌握了它，并且无法实际使用它。但它“优雅地”失败了，因为它回到了默认的颜色上。

Answer 2

我认为可能存在多个问题，请查看绑定表达式错误的“输出窗口”。1)确保文本框在单独的区域内呈现，且不重叠。2)使用相对路径访问控件，并在绑定表达式中使用它的属性

你的转换器看起来很好。

以下是我的xaml

<Window x:Class="StackOverflowBinding.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:stackOverflowBinding="clr-namespace:StackOverflowBinding"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <stackOverflowBinding:ThreadsAvailableCountToColorConverter x:Key="ThreadsAvailableCntConverter"/>
        <stackOverflowBinding: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>

下面是我的代码

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 StackOverflowBinding
{
    /// <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 StackOverflowBinding
{

    [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();
        }
    }
}