How to center nested content in Xamarin Forms StackLayout?

Question

I expect this sample code to create 3 nested blocks with each field centered inside its parent. My understanding is based on What is the difference between LayoutOptions Xamarin.Form, especially Fill and Expand? . Boxes are apparently centered horizontally, but not vertically.

Full repo: https://github.com/pawelpabich/Xamarin-Forms-Nested-Content

Code example:

var mainPage = new ContentPage();

        var content = new StackLayout()
        {
            VerticalOptions = LayoutOptions.Center,
            HorizontalOptions = LayoutOptions.Center,
            BackgroundColor = Color.Yellow,
            HeightRequest = 200,
            WidthRequest = 200,
            Children =
            {
                new StackLayout()
                {
                    BackgroundColor = Color.Blue,
                    HeightRequest = 100,
                    WidthRequest = 100,
                    VerticalOptions = LayoutOptions.Center,
                    HorizontalOptions = LayoutOptions.Center,
                    Children =
                    {
                        new StackLayout()
                        {
                            BackgroundColor = Color.Green,
                            HeightRequest = 50,
                            WidthRequest = 50,
                            VerticalOptions = LayoutOptions.Center,
                            HorizontalOptions = LayoutOptions.Center,
                        }
                    }
                }
            }

        };

        mainPage.Content = content;
        MainPage = mainPage;

The final result, when the application is running in Windows emulator: .

Answer 1

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        var mainPage = new ContentPage();

        var content = new StackLayout()
        {
            VerticalOptions = LayoutOptions.Center,
            HorizontalOptions = LayoutOptions.Center,
            BackgroundColor = Color.Yellow,
            HeightRequest = 200,
            WidthRequest = 200,
            Children =
            {
                new StackLayout()
                {
                    BackgroundColor = Color.Blue,
                    HeightRequest = 100,
                    WidthRequest = 100,
                    VerticalOptions = LayoutOptions.CenterAndExpand,
                    HorizontalOptions = LayoutOptions.Center,
                    Children =
                    {
                        new StackLayout()
                        {
                            BackgroundColor = Color.Green,
                            HeightRequest = 50,
                            WidthRequest = 50,
                            VerticalOptions = LayoutOptions.CenterAndExpand,
                            HorizontalOptions = LayoutOptions.Center,
                        }
                    }
                    }
            }

            };

        mainPage.Content = content;
        MainPage = mainPage; 

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, CenterAndExpand , , "" ( StackLayout ). StackLayout "" , , .