are you missing a using directive or an assembly reference? Error in C#

Question

I'm trying to create a very simple C# program.

Here is the xaml file :

<Window x:Class="HelloWPFApp.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>
        <TextBlock HorizontalAlignment="Left" Margin="104,72,0,0" TextWrapping="Wrap" Text="Select a message option and then choose the Display button" VerticalAlignment="Top"/>
        <RadioButton x:Name="RadioButton1" Content="Hello;" HorizontalAlignment="Left" Margin="104,138,0,0" VerticalAlignment="Top" Checked="RadioButton1_Checked"/>
        <RadioButton x:Name="RadioButton2" Content="Goodbye;" HorizontalAlignment="Left" Margin="342,138,0,0" VerticalAlignment="Top"/>
        <Button Content="Display" HorizontalAlignment="Left" Margin="211,208,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click"/>

    </Grid>
</Window>

Here is the .cs file :

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

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            if (RadioButton1.IsChecked == true)
                MessageBox.Show("Hello");
            else
                MessageBox.Show("Goodbye");

        }
    }
}

And this is the error I get :

'HelloWPFApp.MainWindow' does not contain a definition for 'RadioButton1_Checked' and no extension method 'RadioButton1_Checked' accepting a first argument of type 'HelloWPFApp.MainWindow' could be found (are you missing a using directive or an assembly reference?)

Can you tell me what the problem is?

Answer 1

You have defined an event Handler in your xaml code

 <RadioButton x:Name="RadioButton1" Content="Hello;" HorizontalAlignment="Left" Margin="104,138,0,0" VerticalAlignment="Top" Checked="RadioButton1_Checked"/>

But you have not defined the same in your code-behind. That's what causing the problem. Either remove the Checked Event from the above radio button or define an event handler in your code behind.