WPF RadioButton Example: Checked

RadioButton. A RadioButton offers an option.

It is always visible, and is part of a group of other RadioButtons. One option can be "checked" at a time by the user. We use a RadioButton in WPF, handling its Checked event.

Based on:

.NET 4.5

Example. First, please create a WPF application and drag two RadioButton controls to the window. Next, add the "Checked" attribute to each "RadioButton" element in the XAML. Have Visual Studio create RadioButton_Checked.

Checked: The Checked event is triggered when the user clicks or selects a RadioButton. The "check" is a black circle.

Note: We can have both RadioButton elements point to a single RadioButton_Checked method. Two different methods could instead be used.

In RadioButton_Checked, we access the RadioButton object that raised the event. We cast the "sender" object to a RadioButton type with the as-cast. We then call ToString on its Content property and change the Window Title.

AsProperty

Example markup: XAML

<Window x:Class="WpfApplication16.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>
	<RadioButton Content="Dogs"
		     Checked="RadioButton_Checked"
		     HorizontalAlignment="Left"
		     Margin="10,10,0,0"
		     VerticalAlignment="Top"/>
	<RadioButton Content="Cats"
		     Checked="RadioButton_Checked"
		     HorizontalAlignment="Left"
		     Margin="10,30,0,0"
		     VerticalAlignment="Top"/>
    </Grid>
</Window>

Example code: C#

using System.Windows;
using System.Windows.Controls;

namespace WpfApplication16
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
	public MainWindow()
	{
	    InitializeComponent();
	}

	private void RadioButton_Checked(object sender, RoutedEventArgs e)
	{
	    // ... Get RadioButton reference.
	    var button = sender as RadioButton;

	    // ... Display button content as title.
	    this.Title = button.Content.ToString();
	}
    }
}

Discussion. How can you keep track of which RadioButton is currently checked? One way involves uses a field. Store a field (int, string) on the MainWindow class. And in Checked, assign it to the result of the Content.ToString() method.

Then: You can access this field anywhere (in any method) in your WPF program to determine which RadioButton is checked.

Summary. A CheckBox control may be checked at the same time as another. But only one RadioButton control can be checked. For this reason, a RadioButton can be used to select an exclusive option, such as a program mode.

CheckBox

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