如何将Instanceproperty绑定到viewmodel，视图没有更新

Question

问题：

我的 Viewmodel 创建了一个控制器 mycontroller 的实例，属性 Busy 应传递给 View 并根据控制器状态在 View 中更新，但我的 View 没有得到更新。另一个属性Busy2 根据当前状态更新。 Bindablebase 实现了 I

问题：

为什么 ViewModel 中的属性Busy 没有更新？ mycontroller.Busy 属性正在更新，但视图没有更新。

框架和工具：

棱镜 6.3.0

Fody.Property 已更改

查看：

<TextBlock Text="{Binding Path=Busy}"></TextBlock>
<TextBlock Text="{Binding Path=Busy2}"></TextBlock>

视图模型：

public class Controller
    {
        public bool Busy { get; private set; }

        public async void GetValue()
        {
            Busy = true;
            await Task.Delay(5000);
            Busy = false;
        }
    }

    public class MyViewModel : BindableBase
    {
        private readonly Controller _mycontroller;
        public DelegateCommand<string> RunCommand { get; private set; }

        // This property is not updated in the view
        public bool Busy
        {
            get { return _mycontroller.Busy; }
        }

        // Works as aspected
        public bool Busy2 { get; set; }

        public MyViewModel()
        {
            _mycontroller = new Controller();
            RunCommand = new DelegateCommand<string>(Run, Canrun).ObservesProperty((() => _mycontroller.Busy));
        }

        private bool Canrun(string arg)
        {
            return _mycontroller.Busy != true;
        }

        private void Run(string obj)
        {

            Busy2 = true;
            _mycontroller.GetValue();


        }
    }

更新：

我从 Prism 添加了 Bindablebase，因为它实现了 INotifyPropertyChanged，但视图仍然没有更新。 我重构了代码并设置了一个断点来设置{ SetProperty(ref _busy, value); }，并且从未达到断点。

我也删除了 Propertychanged.Fody nuget 包。

视图模型：

   public class Controller : BindableBase
    {
        private bool _busy;
        public bool Busy
        {
            get { return _busy; }
            set { SetProperty(ref _busy, value); }
        }

        public Controller()
        {

        }

        public void DoWork1()
        {
            for (var i = 0; i < 10; i++)
            {
                Thread.Sleep(1000);
                _busy = !_busy;
                Debug.WriteLine(_busy.ToString());
            }
        }

        public void DoWork2()
        {
            _busy = !_busy;

        }
    }

    public class MainWindowViewModel : BindableBase
    {
        private Controller mycontroller;
        private string _title = "Prism Unity Application";

        public DelegateCommand RunCommand { get; private set; }

        public string Title
        {
            get { return _title; }
            set { SetProperty(ref _title, value); }
        }

        public bool Busy
        {
            get { return mycontroller.Busy; }
        }

        public MainWindowViewModel()
        {
            RunCommand = new DelegateCommand(Execute);
            mycontroller = new Controller();

        }

        private void Execute()
        {
            mycontroller.DoWork1();
        }
    }

查看：

<Window x:Class="PropertytestPrism.Views.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:prism="http://prismlibrary.com/"
        prism:ViewModelLocator.AutoWireViewModel="True"
        Title="{Binding Title}" Height="350" Width="525">
    <StackPanel>
        <Button Command="{Binding RunCommand}" Content="Run"></Button>
        <TextBlock Text="{Binding Busy}"></TextBlock>

    </StackPanel>
</Window>

更新 2

1. 失败：类 Controller 缺少 INotifypropertychanged

View仍然没有更新，原因是我的Delegatecommand方法，它执行了mycontroller.DoWork1();

问题：

为什么视图没有更新？如果我在 DelegateCommand 方法中执行该方法？

Answer 1

您应该通过 Controller 类实现 INotifyPropertyChanged。 Controller 类中的属性发生了变化，应该通知这种变化：

public class Controller : INotifyPropertyChanged
{
    private bool _busy;

    public bool Busy 
    {
        get
        {
            return  _busy;
        } 
        private set
        {
            SetField(ref _busy, value, "Busy"); }
        } 
    }

    public async void GetValue()
    {
        Busy = true;
        await Task.Delay(5000);
        Busy = false;
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;

        if (handler != null)
        {
           handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    protected bool SetField<T>(ref T field, T value, string propertyName)
    {
        if (EqualityComparer<T>.Default.Equals(field, value))
        {
            return false;
        }

        field = value;
        OnPropertyChanged(propertyName);

        return true;
    }
}

Answer 2

试着让你的绑定像这样工作。

<TextBlock Text="{Binding Busy,Mode=OneWay}"></TextBlock>.

默认情况下绑定是一次性的，因此即使在属性更改通知时它们也不会更新。