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.

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.

<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.

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.