回调未正确绑定

Question

在下面的代码中，UnitOccupierDetails 集合正确绑定，但 OwnersCountString 未正确绑定。谁能解释为什么？此代码位于我的 ViewModel 中：

private void BindSelectedStructure(object param) 
    { 
        UnitOccupierDetails.Clear(); 
        Structure selectedStructure = (Structure)param; 
        this.SelectedStructure = selectedStructure; 

        int StructureID = selectedStructure.IDStructure; 
        loadOwners = context.Load<UserOccupier>(context.GetUnitOccupierDetailsQuery(StructureID), OwnersLoadedCallback, false); 
    } 

    private void OwnersLoadedCallback(LoadOperation<UserOccupier> op) 
    { 
        int Counter = 0; 
        foreach (var item in op.Entities) 
        { 
            Counter++; 
            UnitOccupierDetails.Add(item as UserOccupier); 
        } 

        OwnersCountString = "Owners(" + Counter.ToString() + ")"; 
    }

以及 XAML：

     <TextBlock Text='{Binding OwnersCountString,Source={StaticResource ViewModel},Mode=OneWay}'></TextBlock

OwnersCountStringProperty：

private string _ownersCountString;
    public string OwnersCountString
    {
        get { return _ownersCountString; }
        set { _ownersCountString = value; RaisePropertyChanged("OwnersCountString"); }
    }

Answer 1

您的回调未发生在 UI 线程上。这意味着更改正在发生，但 UI 尚未在显示更改的线程上更新自身。

这是我们的示例，来自我的另一个答案。我们的 SendPropertyChanged 版本（替换您的 RaisePropertyChanged）可确保所有代码都在 UI 线程上执行：

protected delegate void OnUiThreadDelegate();

public event PropertyChangedEventHandler PropertyChanged;

public void SendPropertyChanged(string propertyName)
{
    if (this.PropertyChanged != null)
    {
        this.OnUiThread(() => this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName)));
    }
}

protected void OnUiThread(OnUiThreadDelegate onUiThreadDelegate)
{
    if (Deployment.Current.Dispatcher.CheckAccess())
    {
        onUiThreadDelegate();
    }
    else
    {
        Deployment.Current.Dispatcher.BeginInvoke(onUiThreadDelegate);
    }
}