How can I best handle WPF radio buttons?

Question

I've got some RadioButtons in my XAML...

<StackPanel>
    <RadioButton Name="RadioButton1" GroupName="Buttons" Click="ButtonsChecked" IsChecked="True">One</RadioButton>
    <RadioButton Name="RadioButton2" GroupName="Buttons" Click="ButtonsChecked">Two</RadioButton>
    <RadioButton Name="RadioButton3" GroupName="Buttons" Click="ButtonsChecked">Three</RadioButton>
</StackPanel>

And I can handle their click events in the Visual Basic code. This works...

    Private Sub ButtonsChecked(ByVal sender As System.Object, _
                               ByVal e As System.Windows.RoutedEventArgs)
        Select Case CType(sender, RadioButton).Name
            Case "RadioButton1"
                'Do something one
                Exit Select
            Case "RadioButton2"
                'Do something two
                Exit Select
            Case "RadioButton3"
                'Do something three
                Exit Select
        End Select
    End Sub

But, I'd like to improve it. This code fails...

<StackPanel>
    <RadioButton Name="RadioButton1" GroupName="Buttons" Click="ButtonsChecked" Command="one" IsChecked="True">One</RadioButton>
    <RadioButton Name="RadioButton2" GroupName="Buttons" Click="ButtonsChecked" Command="two">Two</RadioButton>
    <RadioButton Name="RadioButton3" GroupName="Buttons" Click="ButtonsChecked" Command="three">Three</RadioButton>
</StackPanel>

    Private Sub ButtonsChecked(ByVal sender As System.Object, _
                               ByVal e As System.Windows.RoutedEventArgs)
        Select Case CType(sender, RadioButton).Command
            Case "one"
                'Do something one
                Exit Select
            Case "two"
                'Do something two
                Exit Select
            Case "three"
                'Do something three
                Exit Select
        End Select
    End Sub

In my XAML I get a blue squiggly underline on the Command= attributes and this tip...

'CommandValueSerializer' ValueSerializer cannot convert from 'System.String'.

In my VB I get a green squiggly underline on the Select Case line and this warning...

Runtime errors might occur when converting 'System.Windows.Input.ICommand' to 'String'.

Even better would be to use Enum type commands with full Intellisense and compile errors rather than runtime errors in case of typos. How can I improve this?

Answer 1

In order for commands to work you need to set up bindings in either your xaml or code behind. These command bindings must reference public static fields that have been previously declared.

Then in your buttons Command attribute you will then need to also reference these same commands.

<Window 
    x:Class="RadioButtonCommandSample.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:RadioButtonCommandSample"
    Title="Window1" 
    Height="300" 
    Width="300"
    >
    <Window.CommandBindings>
        <CommandBinding Command="{x:Static local:Window1.CommandOne}" Executed="CommandBinding_Executed"/>
        <CommandBinding Command="{x:Static local:Window1.CommandTwo}" Executed="CommandBinding_Executed"/>
        <CommandBinding Command="{x:Static local:Window1.CommandThree}" Executed="CommandBinding_Executed"/>
    </Window.CommandBindings>
    <StackPanel>
        <RadioButton Name="RadioButton1" GroupName="Buttons" Command="{x:Static local:Window1.CommandOne}" IsChecked="True">One</RadioButton>
        <RadioButton Name="RadioButton2" GroupName="Buttons" Command="{x:Static local:Window1.CommandTwo}">Two</RadioButton>
        <RadioButton Name="RadioButton3" GroupName="Buttons" Command="{x:Static local:Window1.CommandThree}">Three</RadioButton>
    </StackPanel>
</Window>

public partial class Window1 : Window
{
    public static readonly RoutedCommand CommandOne = new RoutedCommand();
    public static readonly RoutedCommand CommandTwo = new RoutedCommand();
    public static readonly RoutedCommand CommandThree = new RoutedCommand();

    public Window1()
    {
        InitializeComponent();
    }

    private void CommandBinding_Executed(object sender, ExecutedRoutedEventArgs e)
    {
        if (e.Command == CommandOne)
        {
            MessageBox.Show("CommandOne");
        }
        else if (e.Command == CommandTwo)
        {
            MessageBox.Show("CommandTwo");
        }
        else if (e.Command == CommandThree)
        {
            MessageBox.Show("CommandThree");
        }
    }
}