Is there onFocused event in textBox WinUI3 .net?

Question

I need event, that triggers when I focus on textBox. Or it can be Left mouse click event also. I just need to change the text when clicking on the textBox. Does anyone know how to do this?

Answer 1

You can use the GotFocus event.

Sample XAML:

<?xml version="1.0" encoding="utf-8"?>
<Window
    x:Class="App5.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:App5"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center">
        <Button x:Name="myButton1">Button 1</Button>
        <Button x:Name="myButton2">Button 2</Button>
        <Button x:Name="myButton3">Button 3</Button>
        <Button x:Name="myButton4">Button 4</Button>
        <TextBox GotFocus="TextBox_GotFocus"></TextBox>
    </StackPanel>
</Window>

Associated C# code:

using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;

namespace App5
{
    public sealed partial class MainWindow : Window
    {
        public MainWindow()
        {
            this.InitializeComponent();
        }

        private void TextBox_GotFocus(object sender, RoutedEventArgs e)
        {
            (sender as TextBox).Text = "Hello World";
        }
    }
}

Answer 2

You need to access one of the elements that composes the TextBox. This element has no name, and we can only know it as FrameworkElement. To do this, I'm using the FindDescendants extension method from the CommunityToolkit.WinUI.Extensions NuGet package.

private void TextBoxControl_Loaded(object sender, RoutedEventArgs e)
{
    if ((sender as TextBox)?.FindDescendants()
        .Where(x => x.GetType() == typeof(FrameworkElement))
        .FirstOrDefault() is FrameworkElement element)
    {
        element.PointerPressed += Element_PointerPressed;
    }
}

private void Element_PointerPressed(object sender, PointerRoutedEventArgs e)
{
    if (e.Pointer.PointerDeviceType is PointerDeviceType.Mouse &&
        e.GetCurrentPoint(this).Properties.IsLeftButtonPressed is true)
    {
        Debug.WriteLine("Mouse left button pressed.");
    }
}