ComboBox. This WPF control provides a drop-down list of strings. The user clicks on the box, and the items appear. We use properties like ItemsSource and IsEditable.
Getting started. First, we create a new WPF project and drag a ComboBox to the Window. This causes Visual Studio to insert the ComboBox element in the XAML file.
Loaded example. To use the ComboBox, we can add a Loaded event handler for it. This is a good place to initialize. We specify the Loaded and SelectionChanged events.
Tip For event handlers in WPF, please type in the attribute, such as "Loaded" and Visual Studio will create the C# event handler.
Info We use the ComboBox_Loaded event handler to specify the items in the control at runtime.
Detail We do not need to know the items at design-time. We assign a List of strings to the ItemsSource.
Also We set the SelectionIndex property to 0. This sets the first element in the List in the ComboBox.
<Window x:Class="WpfApplication9.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<ComboBox
HorizontalAlignment="Left"
Margin="10,10,0,0"
VerticalAlignment="Top"
Width="120"
Loaded="ComboBox_Loaded"
SelectionChanged="ComboBox_SelectionChanged"/>
</Grid>
</Window>using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
namespace WpfApplication9
{
/// <summary>/// Interaction logic for MainWindow.xaml/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void ComboBox_Loaded(object sender, RoutedEventArgs e)
{
// ... A List.
List<string> data = new List<string>();
data.Add("Book");
data.Add("Computer");
data.Add("Chair");
data.Add("Mug");
// ... Get the ComboBox reference.
var comboBox = sender as ComboBox;
// ... Assign the ItemsSource to the List.
comboBox.ItemsSource = data;
// ... Make the first item selected.
comboBox.SelectedIndex = 0;
}
private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
// ... Get the ComboBox.
var comboBox = sender as ComboBox;
// ... Set SelectedItem as Window Title.
string value = comboBox.SelectedItem as string;
this.Title = "Selected: " + value;
}
}
}
SelectionChanged. We also use the ComboBox_SelectionChanged event handler. We display the currently selected item in the ComboBox as part of the Window Title.
ItemsSource. The ItemsSource is a property on the ComboBox. It can be assigned to any reference object that implements the IEnumerable interface.
Info IEnumerable includes arrays and Lists. We can set all the items in a single assignment.
Also We can read in the items from a text file containing strings, and then use those values (stored in a List or array) as the items.
A summary. A ComboBox presents the user with a choice. We populate the ComboBox with the ItemsSource property. And in event handlers (SelectionChanged) we act on user input.
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This page was last updated on Sep 29, 2022 (edit).