C# 为什么PropertyChangedEvent对一个AttachedProperty只开火一次

OnShouldRefreshPropertyChanged仅触发一次，并且在更改NeedsRefresh的值时不会触发。有人能解释一下发生了什么事吗？我使用的Datagrid来自.NET3.5的WPFToolKit，尽管我认为这并不重要

行为：

public static class DataGridRefreshBehavior
{
    // Using a DependencyProperty as the backing store for ShouldRefresh.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty ShouldRefreshProperty =
        DependencyProperty.RegisterAttached("ShouldRefresh",
        typeof(bool),
        typeof(DataGridRefreshBehavior),
        new UIPropertyMetadata(false, OnShouldRefreshPropertyChanged));

    public static void SetShouldRefresh(DependencyObject obj, bool value)
    {
        if (obj != null)
            obj.SetValue(ShouldRefreshProperty, value);
    }

    public static bool GetShouldRefresh(DependencyObject obj)
    {
        if (obj != null)
            return (bool)obj.GetValue(ShouldRefreshProperty);
        else
            return false;
    }

    private static void OnShouldRefreshPropertyChanged(object sender, DependencyPropertyChangedEventArgs e)
    {
        var attachedObject = sender as DataGrid;
        if (attachedObject != null)
        {
            bool needsRefresh = (bool)e.NewValue;
            if (needsRefresh)
            {
                attachedObject.Items.Refresh();
            }
        }
    }
}

local:DataGridRefreshBehavior.ShouldRefresh="{Binding Path=NeedsRefresh,UpdateSourceTrigger=PropertyChanged}"

public bool NeedsRefresh
    {
        get
        {
            return needsRefresh;
        }
        set
        {

            needsRefresh = value;
            NotifyOfPropertyChange(() => NeedsRefresh);

        }
    }

Xaml:

public static class DataGridRefreshBehavior
{
    // Using a DependencyProperty as the backing store for ShouldRefresh.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty ShouldRefreshProperty =
        DependencyProperty.RegisterAttached("ShouldRefresh",
        typeof(bool),
        typeof(DataGridRefreshBehavior),
        new UIPropertyMetadata(false, OnShouldRefreshPropertyChanged));

    public static void SetShouldRefresh(DependencyObject obj, bool value)
    {
        if (obj != null)
            obj.SetValue(ShouldRefreshProperty, value);
    }

    public static bool GetShouldRefresh(DependencyObject obj)
    {
        if (obj != null)
            return (bool)obj.GetValue(ShouldRefreshProperty);
        else
            return false;
    }

    private static void OnShouldRefreshPropertyChanged(object sender, DependencyPropertyChangedEventArgs e)
    {
        var attachedObject = sender as DataGrid;
        if (attachedObject != null)
        {
            bool needsRefresh = (bool)e.NewValue;
            if (needsRefresh)
            {
                attachedObject.Items.Refresh();
            }
        }
    }
}

local:DataGridRefreshBehavior.ShouldRefresh="{Binding Path=NeedsRefresh,UpdateSourceTrigger=PropertyChanged}"

public bool NeedsRefresh
    {
        get
        {
            return needsRefresh;
        }
        set
        {

            needsRefresh = value;
            NotifyOfPropertyChange(() => NeedsRefresh);

        }
    }

视图模型：

public static class DataGridRefreshBehavior
{
    // Using a DependencyProperty as the backing store for ShouldRefresh.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty ShouldRefreshProperty =
        DependencyProperty.RegisterAttached("ShouldRefresh",
        typeof(bool),
        typeof(DataGridRefreshBehavior),
        new UIPropertyMetadata(false, OnShouldRefreshPropertyChanged));

    public static void SetShouldRefresh(DependencyObject obj, bool value)
    {
        if (obj != null)
            obj.SetValue(ShouldRefreshProperty, value);
    }

    public static bool GetShouldRefresh(DependencyObject obj)
    {
        if (obj != null)
            return (bool)obj.GetValue(ShouldRefreshProperty);
        else
            return false;
    }

    private static void OnShouldRefreshPropertyChanged(object sender, DependencyPropertyChangedEventArgs e)
    {
        var attachedObject = sender as DataGrid;
        if (attachedObject != null)
        {
            bool needsRefresh = (bool)e.NewValue;
            if (needsRefresh)
            {
                attachedObject.Items.Refresh();
            }
        }
    }
}

local:DataGridRefreshBehavior.ShouldRefresh="{Binding Path=NeedsRefresh,UpdateSourceTrigger=PropertyChanged}"

public bool NeedsRefresh
    {
        get
        {
            return needsRefresh;
        }
        set
        {

            needsRefresh = value;
            NotifyOfPropertyChange(() => NeedsRefresh);

        }
    }

---

它是根本没有发射还是

e.NewValue

返回为

false

？。

NotiyfOfPropertyChange（…）

在做什么？您通常必须在代码中指定

DependencyPropertyChangedEventArgs

的值，您是否曾经手动设置/更新

ShouldRefresh

属性（通过调用

SetShouldRefresh（）

）？这将破坏绑定（默认为单向），并忽略对

NeedsRefresh

的进一步更改。尝试将绑定模式设置为双向，看看是否有帮助：

。Path=NeedsRefresh，mode=TwoWay..

。它第一次激发，然后甚至不激发，我不是手动调用SetShouldRefresh，我所做的就是调用NeedsRefresh=true。NotipfyPropertyChange类似于OnPropertyChanged（“NeedsRefresh”），您只设置了

NeedRefresh=true

？您需要在设置为true和false之间进行切换，因此值实际上会发生更改。我的印象是，如果调用NotifyPropertyChanged，则无论值是否实际更改，都将读取该值。谢谢你帮我认识到我的愚蠢，我现在就躲到地下室去：）