WPF ProgressBar未使用INotifyPropertyChanged进行更新

Question

我有一个带有几个TextBox控件和ProgressBar的UserControl。 TextBox控件正确地反映了它们绑定到的代码隐藏中的属性。但是，ProgressBar不响应属性更改。

我的XAML：

<UserControl
             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:Controls="clr-namespace:Cmc.Installer.Controls;assembly=Cmc.Installer.Controls" x:Class="Cmc.Installer.Modules.MobileRecruiter.MobileRecruiterModule" 
             mc:Ignorable="d" 
             d:DesignHeight="600" d:DesignWidth="800">
    <Grid HorizontalAlignment="Left" Height="580" Margin="10,10,0,0" VerticalAlignment="Top" Width="780">
        <Canvas>
            <Label Content="Database Server" HorizontalAlignment="Left" Margin="10,10,0,0" VerticalAlignment="Top"/>
            <TextBox Text="{Binding DatabaseServer}" Height="23" Canvas.Left="160" Canvas.Top="12" Width="160"/>
            <Label Content="Database Name" HorizontalAlignment="Left" VerticalAlignment="Top" Canvas.Left="10" Canvas.Top="38"/>
            <TextBox Text="{Binding DatabaseName}" Height="23" Canvas.Left="160" Canvas.Top="40" Width="160"/>
            <Label Content="Database Username" HorizontalAlignment="Left" VerticalAlignment="Top" Canvas.Left="10" Canvas.Top="66"/>
            <TextBox Text="{Binding DatabaseUsername}" Height="23" Canvas.Left="160" Canvas.Top="68" Width="160"/>
            <Label Content="Database Password" HorizontalAlignment="Left" VerticalAlignment="Top" Canvas.Left="10" Canvas.Top="94"/>
            <Controls:BindablePasswordBox Password="{Binding DatabasePassword}" Height="23" Canvas.Left="160" Canvas.Top="96" Width="160"/>
            <ProgressBar Name="ProgressBar" Value="{Binding Progress}" Minimum="0" Maximum="100" Canvas.Left="10" Canvas.Top="164" Width="760" Height="24" />
        </Canvas>
    </Grid>
</UserControl>

它的代码隐藏（非常简略）：

public partial class MobileRecruiterModule : UserControl, INotifyPropertyChanged
{
    private static readonly Logger Logger = LogManager.GetCurrentClassLogger();
    private int _progress;

    public MobileRecruiterModule()
    {
        InitializeComponent();
        DataContext = this;
    }

    public string DatabaseServer { get; set; }
    public string DatabaseName { get; set; }
    public string DatabaseUsername { get; set; }
    public string DatabasePassword { get; set; }

    public int Progress
    {
        get { return _progress; }
        set
        {
            if (value == _progress) return;
            _progress = value;
            OnPropertyChanged("Progress");
            Logger.Trace("Progress.set() = " + _progress);
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(string name)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(name));
        }
    }

    // This is called by an external class
    public void OnProgressChanged(object sender, ProgressChangedEventArgs args)
    {
        Progress = args.ProgressPercentage;
    }

}

我知道Progress的价值正在发生变化，因为我在NLog日志中看到了它：

2014-04-17 16:22:54.4068|TRACE|Cmc.Installer.Modules.MobileRecruiter.MobileRecruiterModule|Progress.set() = 28

我不明白为什么ProgressBar在记录调用之前在setter中触发OnPropertyChanged时不会更新。

Answer 1

我以MVVM模式复制了你的应用程序的缩小版本，并祝你好运。我使用此代码复制您的用户控件...

<UserControl x:Class="ProgressBarBinding.Login"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Grid HorizontalAlignment="Left" Height="580" Margin="10,10,0,0" VerticalAlignment="Top" Width="780">
        <Canvas>
            <Label Content="Database Server" HorizontalAlignment="Left" Margin="10,10,0,0" VerticalAlignment="Top"/>
            <TextBox Text="{Binding DatabaseServer}" Height="23" Canvas.Left="160" Canvas.Top="12" Width="160"/>
            <Label Content="Database Name" HorizontalAlignment="Left" VerticalAlignment="Top" Canvas.Left="10" Canvas.Top="38"/>
            <TextBox Text="{Binding DatabaseName}" Height="23" Canvas.Left="160" Canvas.Top="40" Width="160"/>
            <Label Content="Database Username" HorizontalAlignment="Left" VerticalAlignment="Top" Canvas.Left="10" Canvas.Top="66"/>
            <TextBox Text="{Binding DatabaseUsername}" Height="23" Canvas.Left="160" Canvas.Top="68" Width="160"/>
            <Label Content="Database Password" HorizontalAlignment="Left" VerticalAlignment="Top" Canvas.Left="10" Canvas.Top="94"/>
            <ProgressBar Name="ProgressBar" Value="{Binding Progress}" Minimum="0" Maximum="100" Canvas.Left="10" Canvas.Top="164" Width="760" Height="24" />
        </Canvas>
    </Grid>
</UserControl>

唯一缺少的是您的专有密码控制，这不会影响解决方案。

我将此控件编码为MainWindow.xaml文件，因此......

<Window x:Class="ProgressBarBinding.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="clr-namespace:ProgressBarBinding"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <vm:ViewModel x:Key="ViewModel"/>
    </Window.Resources>
    <Grid DataContext="{StaticResource ViewModel}">
        <vm:Login/>
    </Grid>
</Window> 

请注意，窗口资源定义包括对视图模型实例的引用。大多数人使用依赖注入设置MVVM，但这种方法适用于快速试用和 Indicative Code 。视图模型被设置为网格的数据上下文。 您的控件从网格继承数据上下文。这是xaml代码的结尾。除了调用InitializeComponent（以及创建VM实例的那些）之外，MainWindow.xaml.cs文件中没有代码隐藏。

ViewModel类看起来像这样......

public class ViewModel : INotifyPropertyChanged
{
    private readonly SynchronizationContext _synchronizationContext = SynchronizationContext.Current;
    public ViewModel()
    {
        DatabaseServer = "AnyServer";
        DatabaseName = "Any name";
        Model m = new Model();
        Task.Run(() => m.DoWork(this));
    }
    public string DatabaseServer { get; set; }
    public string DatabaseName { get; set; }
    public string DatabaseUsername { get; set; }
    public string DatabasePassword { get; set; }
    private int _progress;
    public int Progress
    {
        get { return _progress; }
        set
        {
            if (value == _progress) return;
            _progress = value;
            OnPropertyChanged("Progress");
            Console.WriteLine(@"Progress.set() = " + _progress);
        }
    }
    // This is called by an external class
    public void OnProgressChanged(object sender, ProgressChangedEventArgs args)
    {
        _synchronizationContext.Send(delegate { Progress = args.ProgressPercentage; }, null);
    }
    #region INotifyPropertyChanged Implementation
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged(string name)
    {
        var handler = Interlocked.CompareExchange(ref PropertyChanged, null, null);
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(name));
        }
    }
    #endregion
}

除了UI元素没有依赖关系外，视图模型中的大多数代码看起来都像你的。一切都是通过绑定完成的。我在回调中使用了SynchronizationContext，尽管在您的应用程序中可能没有必要。

VM的构造函数在TPL线程上启动模型。模型看起来像这样......

public class Model
{
    public void DoWork(ViewModel vm)
    {
        int progressPercentage = 0;
        for (int i = 0; i < 100000; i++)
        {
            vm.OnProgressChanged(this, new ProgressChangedEventArgs(progressPercentage, null));
            if (i%1000 == 0)
            {
                ++progressPercentage;
            }
        }
    }
}

因此，将所有内容放在一起，模型在其自己的线程中运行，并且UI正在其自己的线程上进行更新。整个过程按预期工作。

ProgressBar将增加到100，并且在模型正在运行时UI将保持响应。这个答案并没有解释为什么你的原始代码不起作用，但我怀疑它与UI线程被淘汰有关。您可以通过完整的日志历史记录来证明这一点，但UI上没有任何变化。总的来说，这个答案正朝着其他人在评论中提出的方式发展：即MVVM绑定方法有很多可以提供。

Answer 2

由于您在UserControl中，您需要明确地为其命名并在绑定时使用 ElementName 标记，如下所示：

<UserControl
             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:Controls="clr-namespace:Cmc.Installer.Controls;assembly=Cmc.Installer.Controls" x:Class="Cmc.Installer.Modules.MobileRecruiter.MobileRecruiterModule" 
             mc:Ignorable="d" 
             d:DesignHeight="600" d:DesignWidth="800" x:Name="MyControl">
    <Grid HorizontalAlignment="Left" Height="580" Margin="10,10,0,0" VerticalAlignment="Top" Width="780">
        <Canvas>
            <ProgressBar Name="ProgressBar" Value="{Binding Progress, ElementName=MyControl}" Minimum="0" Maximum="100" Canvas.Left="10" Canvas.Top="164" Width="760" Height="24" />
        </Canvas>
    </Grid>
</UserControl>

Answer 3

如果您拥有Binding，为什么需要Actual control。由于您未在MVVM中执行此操作，只需立即致电ProgressBar。

ProgressBar.Dispatcher.Invoke(() => ProgressBar.Value = Progress = args.ProgressPercentage);

很抱歉，如果您的Binding课程中可以访问所有属性/控件，我就无法看到View的好处。

如果您实施了MVVM，那么绑定会更有用，更强大。