Question

我有这个组合框：

<ComboBox ItemsSource="{Binding Knobs.AvailableFlightModes}" 
    SelectedValue="{Binding Knobs.FlightMode}" SelectedValuePath="Value" />

数据上下文实现INotifyPropertyChanged接口，并在代码中检查所选的FlightMode是否正常，如果不是，我会更改它。问题是，当我将其更改回显示的项目时，将更改回来。例如：所选项目为item1，用户将其更改为item2，并将其更改回item1，但显示仍为item2。

这是一个示例代码：

public class Names : INotifyPropertyChanged 
{
    public Names()
    {
        m_NewList = new ObservableCollection<thing>();
        foreach (things item in Enum.GetValues(typeof(things)))
        {
            m_NewList.Add(new thing() { Enum = item });
        }

        this.PropertyChanged += new PropertyChangedEventHandler(Names_PropertyChanged);
    }

    public event PropertyChangedEventHandler PropertyChanged;

    void Names_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == "Stuff" && m_Stuff != things.a)
        {
            Stuff = things.a;
        }
    }

    private readonly ObservableCollection<thing> m_NewList;
    public ObservableCollection<thing> NewList { get { return m_NewList; } }

    private things m_Stuff;
    public things Stuff
    {
        get { return m_Stuff; }
        set
        {
            m_Stuff = value;
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs("Stuff"));
        }
    }
}

public class thing
{
    public things Enum { get; set; }
    public string Just { get; set; }
    public override string ToString()
    {
        return Enum.ToString();
    }
}

public enum things { a, b, c, d }

-

<ComboBox ItemsSource="{Binding NewList}" SelectedValuePath="Enum" SelectedValue="{Binding Stuff}" />

Answer 1

我看到了问题。出于某种原因，当绑定框架已经在通知内部时，它似乎忽略了属性更改通知。

作为一种解决方法，您可以通过异步执行来推迟属性更改。这符合预期。

void Names_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
    Dispatcher.CurrentDispatcher.BeginInvoke(new Action(() =>
    {
        if (e.PropertyName == "Stuff" && m_Stuff != things.a)
        {
            Stuff = things.a;
        }
    }));
}

Answer 2

确保在Knobs对象上设置FlightMode属性时调用NotifyPropertyChanged（“FlightMode”）。

Combobox项目不会更新

2 个答案: