dynamically assigning an event

I am dynamically creating a GroupBox and trying to assign the MouseLeftButtonDow开发者_JS百科n event to it to perform some action when the user left-clicks on it. This is what I've tried:

public MyClass()
{
    tagGroupBox.MouseLeftButtonDown += new MouseButtonEventHandler(tagGroupBox_MouseLeftButtonDown);  //generates error: "tagGroupBox_MouseLeftButtonDown does not exist in the current context"
}

private void tagGroupBox__MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
     MessageBox.Show("Left click event triggered");
}

There are __ (double underscores) in handler method.

void tagGroupBox_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
}

This works for me:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        GroupBox g = new GroupBox();
        g.MouseLeftButtonUp += new MouseButtonEventHandler(g_MouseLeftButtonUp);
        MainGrid.Children.Add(g);
    }

    void g_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        System.Diagnostics.Debugger.Break();
    }
}

XAML

<Window x:Class="WpfApplication1.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 x:Name="MainGrid">

    </Grid>
</Window>