Universal Windows Platform (UWP) -simple example UWP app written in C#

Universal Windows Platform (UWP) allows you to build apps that can run on various Windows devices. Here's a simple example of a UWP app written in C#. This sample app will display a button, and when clicked, it will show a message dialog.

### Step-by-Step Guide

1. **Install Visual Studio**: Ensure you have Visual Studio installed with the UWP development workload.

2. **Create a New UWP Project**:
   - Open Visual Studio.
   - Click on `Create a new project`.
   - Search for `Blank App (Universal Windows)`, select it, and click `Next`.
   - Name your project, choose a location, and click `Create`.
   - Select the target and minimum versions of Windows, then click `OK`.

3. **Add UI Elements**:
   - Open `MainPage.xaml`.
   - Replace the existing XAML code with the following:

```xml

<Page

    x:Class="MyUWPApp.MainPage"

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    xmlns:local="using:MyUWPApp"

    xmlns: d="http://schemas.microsoft.com/expression/blend/2008"

    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

    mc:Ignorable="d">

    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

        <Button x:Name="myButton" Content="Click Me" HorizontalAlignment="Center" VerticalAlignment="Center" Click="MyButton_Click"/>

    </Grid>

</Page>

```

4. **Add Click Event Handler**:
   - Open `MainPage.xaml.cs`.
   - Replace the existing code with the following:

```csharp
using Windows.UI.Popups;
using Windows.UI.Xaml.Controls;

namespace MyUWPApp
{
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
        }

        private async void MyButton_Click(object sender, Windows.UI.Xaml.RoutedEventArgs e)
        {
            var messageDialog = new MessageDialog("Hello, UWP!");
            await messageDialog.ShowAsync();
        }
    }
}
```

5. **Run the App**:
   - Press `F5` to build and run the app.
   - Click the "Click Me" button, and a message dialog with "Hello, UWP!" will appear.

### Explanation

- **MainPage.xaml**: This file defines the user interface. A `Button` is placed in the center of the page.
- **MainPage.xaml.cs**: This file contains the code-behind for the XAML file. It defines the event handler `MyButton_Click` which gets called when the button is clicked. The event handler shows a message dialog with the text "Hello, UWP!".

This simple UWP app demonstrates the basics of creating a UI, handling events, and displaying a message. You can expand on this by adding more UI elements, handling other events, and incorporating more complex logic.