更改事件处理程序的属性

我希望进度条在下载完成之前一直可见。

为了做到这一点，我将"Visibility"属性与一个名为"loadBarVisibility"的属性绑定。

XAML代码：

<ProgressBar Visibility="{Binding loadBarVisibility}" IsIndeterminate="True"/>

ViewModel代码：

public class MainViewModel : ViewModelBase
{
    public static Visibility loadBarVisibility { get; set; }
    private const String URL = "myurl";

    public MainViewModel()
    {
        loadFlux();

        if (IsInDesignMode)
        {
            // Code runs in Blend --> create design time data.
        }
        else
        {
            // Code runs "for real"
        }
    }

    public static void loadFlux()
    {
        loadBarVisibility = Visibility.Visible;
        WebClient client = new WebClient();
        client.DownloadStringAsync(new Uri(URL));
        client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(test_downloadFinished);

    }

    public static void test_downloadFinished(object sender, DownloadStringCompletedEventArgs e)
    {
        if (e.Error == null)
        {
            loadBarVisibility = Visibility.Collapsed;
        }
    }
}

但是上面的代码不起作用：进度条仍然可见。

否则，当我在"client.DownloadStringCompleted+=new DownloadStringCompletedEventHandler（test_downloadFinished）；"之后放入"loadBarVisibility=Visibility。Collapsed；"时，它就起作用了

有办法解决我的问题吗？

非常感谢。