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WPF ComboBox Example (ItemsSource)

Use the WPF ComboBox control with the ItemsSource property in C# code.
ComboBox. This is a drop-down list of strings. The user clicks on the box, and the items appear. We set items with ItemsSource. With IsEditable, the ComboBox accepts input text.
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. We then 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.

Loaded. We use the ComboBox_Loaded event handler to specify the items in the control at runtime. 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.

Example markup: XAML <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> Example code: C# 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. The string could be used in any way in the C# code.
ItemsSource. The ItemsSource is a property on the ComboBox. It can be assigned to any reference object that implements the IEnumerable interface. This includes arrays and Lists. We can set all the items in a single assignment.PropertyIEnumerableArray

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.

Summary. A ComboBox presents the user with a choice. We populate the ComboBox in various ways. The ItemsSource property is one of the easiest—it receives an IEnumerable collection. And in event handlers (SelectionChanged) we act on user input.
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