Recursive Directory Search

This is a recursive function I wrote that returns an ArrayList of the file names in a folder. This was written in VisualBasic.net 2015.

       Private Function recursiveDirectorySearch(ByVal SearchDirectory As String, ByRef Optional SearchPattern As String = "*.pdf") As ArrayList
        Dim Directory, CurrentFile As String
        Dim myList As New ArrayList
        Try
            For Each Directory In System.IO.Directory.GetDirectories(SearchDirectory)
                For Each CurrentFile In System.IO.Directory.GetFiles(Directory, SearchPattern)
                    myList.Add(CurrentFile)
                Next
                Dim tempArrayList As ArrayList = recursiveDirectorySearch(Directory.ToString, SearchPattern.ToString)
                For Each tempFile As String In tempArrayList
                    myList.Add(tempFile)
                Next
            Next
            Return myList
        Catch ex As System.Exception
            Throw ex
        End Try