KeyDown Event Handler
This page was last reviewed on Sep 27, 2022.
Dot Net Perls
KeyDown. Applications sometimes need to access keyboard commands. With the KeyDown event handler (in C# code) we can listen for key presses, like "function keys" like F5 for example.
Getting started. Let us begin with a new WPF program. Please add a KeyDown event handler to the Window element. Let Visual Studio create Window_KeyDown by pressing Enter.
Example code. Here we add some code to the event handler. In the Window_KeyDown method, the KeyEventArgs is important. From it, we access the key that was pressed.
Detail This is the property that tells us what key was pressed. In this example, we test against the Key.F5 constant.
Tip When the user presses F5, the window title will change to a special message. In many programs, like web browsers, F5 means "reload."
<Window x:Class="WpfApplication25.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" KeyDown="Window_KeyDown"> </Window>
using System.Windows; using System.Windows.Input; namespace WpfApplication25 { /// <summary> /// Interaction logic for MainWindow.xaml /// </summary> public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); } private void Window_KeyDown(object sender, KeyEventArgs e) { // ... Test for F5 key. if (e.Key == Key.F5) { this.Title = "You pressed F5"; } } } }
KeyBinding. More complicated key presses are handled with "gestures" in WPF. We can specify commands with KeyBinding elements. On MenuItems, we can specify InputGestureText.
And With a simple KeyDown method, we cannot easily handle complex commands. A KeyBinding is needed.
Summary. With KeyDown, we add keyboard commands to WPF programs. We used the Key property to test a KeyEventsArg object. For complex keyboard requirements, KeyBindings are needed.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Sep 27, 2022 (edit).
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