ContentDialog 未与 UWP 中心对齐

据我所知，ContentDialog的默认行为应该是使其在 PC 上居中并在移动设备上与顶部对齐，但就我而言，即使在 PC 上我也将其与顶部对齐，但我不明白发生了什么。

我正在使用代码隐藏来创建它，这是我正在使用的代码片段：

// Creates the password box
var passwordBox = new PasswordBox {IsPasswordRevealButtonEnabled = true, Margin = new Thickness(5)};            

// Creates the StackPanel with the content
var contentPanel = new StackPanel();
contentPanel.Children.Add(new TextBlock
{
    Text = "Insert your password to access the application",
    Margin = new Thickness(5),
    TextWrapping = TextWrapping.WrapWholeWords
});
contentPanel.Children.Add(passwordBox);       

// Creates the password dialog
_passwordDialog = new ContentDialog
{
    PrimaryButtonText = "accept",
    IsPrimaryButtonEnabled = false,
    SecondaryButtonText = "exit",
    Title = "Authentication",
    Content = contentPanel
};

// Report that the dialog has been opened to avoid overlapping
_passwordDialog.Opened += (s, e) =>
{
    // HACK - opacity set to 0 to avoid seeing behind dialog
    Window.Current.Content.Opacity = 0;
    _canShowPasswordDialog = false;
};
// Report that the dialog has been closed to enable it again
_passwordDialog.Closed += (s, e) =>
{
    // HACK - opacity set to 1 to reset the window to original options
    Window.Current.Content.Opacity = 1;
    _canShowPasswordDialog = true;
};

// Clear inserted password for next logins
_passwordDialog.PrimaryButtonClick += (s, e) =>
{
    // ... login ...
};

// Close the app if the user doesn't insert the password
_passwordDialog.SecondaryButtonClick += (s, e) => { BootStrapper.Current.Exit(); };

// Set the binding to enable/disable the accept button 

_passwordDialog.SetBinding(ContentDialog.IsPrimaryButtonEnabledProperty, new Binding
{
    Source = passwordBox,
    Path = new PropertyPath("Password"),
    Mode = BindingMode.OneWay,
    Converter = new PasswordValidatorConverter()
});

我已经尝试过使用VerticalAlignment and FullSizeDesired但我没有得到预期的结果。

我怎样才能解决这个问题？

The ContentDialog就像Popup控制, 的PopupRoot当它显示在页面上时保留它。但与Popup控制，放置的位置ContentDialog是写在后面的代码中的，并且这个属性没有暴露给我们，我们无法改变它。

据我所知，ContentDialog的默认行为应该是让它以PC为中心。

The ContentDialog并不总是以PC为中心。我测试了ContentDialog基于您发布的代码。这ContentDialog当页面高度小于 640 时，与页面顶部对齐。当页面高度等于 640 或大于 640 时，与页面居中。

从上图中我们可以看到放置的位置ContentDialog由高度触发Page.