Recursively walking through a directory tree and listing file names

I'm trying to walk through a whole directory tree and print out all the file names on a listbox control. I wrote some code but there are errors. Not sure what I'm doing wrong. By the way, this is in C# using WPF in Visual Studio.

Here is the whole project solution in Visual Studio: http://tinyurl.com/a2r5jv9

Here is the code from MainWindow.xaml.cs if you don't want to download the project solution: http://pastebin.com/cWRTeq3N

I'll paste the code here as well.

public partial class MainWindow : Window
{
    private void Button_Click_1(object sender, RoutedEventArgs e)
    {
        string sourcePath = @"C:\temp\";            

        static void DirSearch(string sourcePath)
        {
            try
            {
                foreach (string d in Directory.GetDirectories(sourcePath))
                {
                    foreach (string f in Directory.GetFiles(d))
                    {
                        listBox1.Items.Add(f);
                    }
                    DirSearch(d);
                }
            }                      
            catch (Exception ex)
            {
                listBox1.Items.Add(ex.Message);
            }
        }
    }
}