尝试在你的 MainPage 的 constructor 中设置 PreferredLaunchViewSize 像这样:

Try setting PreferredLaunchViewSize in your MainPage's constructor like this:

public MainPage()
{
    this.InitializeComponent();

    ApplicationView.PreferredLaunchViewSize = new Size(480, 800);
    ApplicationView.PreferredLaunchWindowingMode = ApplicationViewWindowingMode.PreferredLaunchViewSize;
}

正如@kol 还指出的，如果您想要任何小于默认 500x320 的尺寸，您需要手动重置它:

As @kol also pointed out, if you want any size smaller than the default 500x320, you will need to manually reset it:

ApplicationView.GetForCurrentView().SetPreferredMinSize(new Size(200, 100));