Primes 2.0

Using the Visual Studio integrated development environment and the C# programming language, we will develop a cross-platform mobile application to generate a sequence of prime numbers.

Information

A prime number is a natural number greater than 1 that is not a product of two smaller natural numbers.

• Source: Wikipedia

Start

1. Launch the Visual Studio integrated development environment.

2. Create a new project: Visual C# > Cross-Platform > Mobile App (Xamarin.Forms).

3. Name the project: Primes 2.0.

MainPage.xaml

The MainPage.xaml file contains the source code for the application's user interface design and is written in XAML. Copy (Ctrl+C) and paste (Ctrl+V) the fragment below into your application

<!-- User Interface (UI): Primes 2.0 -->
<StackLayout Padding="20" BackgroundColor="Yellow">
        
    <!-- Title -->
    <Label Text="Primes 2.0" FontSize="Large" />

    <!-- Limit -->
    <Label Text="Limit" />
    <Entry x:Name="boxLimit" Keyboard="Numeric" Text="1000" />
    <Button Text="Generate" Clicked="OnButtonClicked" />
        
    <!-- Numbers -->
    <ListView x:Name="boxNumbers" />
        
</StackLayout>

MainPage.xaml.cs

The MainPage.xaml.cs file contains the source code for the application's business logic and is written in C#. Copy (Ctrl+C) and paste (Ctrl+V) the fragment below into your application.

// Business Logic (BL): Primes 2.0
public partial class MainPage : ContentPage
{
        // Constructor
        public MainPage()
        {
            InitializeComponent();
        }

        // Button Click Event Handler
        void OnButtonClicked(object sender, EventArgs args)
        {
            List<int> primes = new List<int>();
            int limit = int.Parse(this.boxLimit.Text);
            for (int k = 2; k < limit; k++)
            {
                bool prime = true;
                for (int j = 2; j < k; j++) if (k % j == 0) prime = false;
                if (prime) primes.Add(k);
            }
            this.boxNumbers.ItemsSource = primes;
        }
}

Demo

Run the application from the menu: Debug > Start Debugging or by pressing the F5 key.

Fig. 2.59 Testing the cross-platform mobile application for generating a sequence of prime numbers - Android Emulator 11 (API 30)