如何改变Shell.TitleView的高度？

<Application.Resources>
    <Style x:Key="CustomShellStyle" TargetType="Shell">
        <Setter Property="TitleView">
            <Setter.Value>
                <Grid HeightRequest="50">
                    <!-- 在这里添加你自定义的TitleView内容 -->
                </Grid>
            </Setter.Value>
        </Setter>
    </Style>
</Application.Resources>

public App()
{
    InitializeComponent();

    MainPage = new Shell();
    Shell.SetStyle(MainPage, (Style)Application.Current.Resources["CustomShellStyle"]);
}