I have this code that searches a directory:

Code:
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        ' make a reference to a directory
        Dim di As New IO.DirectoryInfo("c:\")
        Dim diar1 As IO.FileInfo() = di.GetFiles()
        Dim dra As IO.FileInfo

        'list the names of all files in the specified directory
        For Each dra In diar1
            ListBox1.Items.Add(dra)
        Next
    End Sub
How do I make it so that it includs subdirectories?