列表框的Windows Phone 7空数据消息？

Question

好的，所以我试图在集合为空时显示一条非常简单的消息。在我第二次访问之后，它只在一个数据透视页面项目上工作...真的想要一个优雅的解决方案。感觉我在这里错过了一些非常简单的东西。

在我的ViewModel ...

中

    private bool _IsDataLoaded;
    public bool IsDataLoaded
    {
        get
        {
            return _IsDataLoaded;
        }
        set
        {
            _IsDataLoaded = value;
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs("IsDataLoaded"));
            }
        }
    }

    public string EmptyMessage
    {
        get
        {
            if (IsDataLoaded)
            {
                return "No Tips for this Venue.";
            }
            else
            {
                return "";
            }
        }
    }

    ........

     void clientGetTips_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
    {
        ...

        this.IsDataLoaded = true;
    }

这是xaml ....

    <TextBlock Text="{Binding EmptyMessage}" Visibility="{Binding Converter={StaticResource CollectionLengthToVisibilityConverter1}, Path=VitalSigns.Count}" FontSize="{StaticResource PhoneFontSizeExtraLarge}" />

Answer 1

您还需要为EmptyMessage引发更改事件，如下所示：

public bool IsDataLoaded
{
    get
    {
        return _IsDataLoaded;
    }
    set
    {
        _IsDataLoaded = value;
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs("IsDataLoaded"));
            PropertyChanged(this, new PropertyChangedEventArgs("EmptyMessage"));
        }
    }
}