Vb.net error when calling Oracle stored procedure with an out paramter using Microsoft Oracle Managed Data Provider

I'm using VB.Net to connect to Oracle with the Mocrosoft managed data provider for Oracle.  I can connect to the database and run a query and get data back with no problem.  Now I need to call a stored procedure thate has 2 paramters.  The first one is a varchar input paramter and the second one is a number output parameter.  My code is below.  When the app gets to the myCommand.ExecuteNonQuery() statement I get the following error:

An unhandled exception of type 'System.Data.OracleClient.OracleException' occurred in system.data.oracleclient.dll

Additional information: System error.

The examples I've found match my syntax and I've got no clue what else to try.

        Dim document_id As Integer
        Dim myConnection As New OracleConnection
        Dim myCommand As New OracleCommand

        connString = "data source=HOLMES;user id=LINE_HOST;password=LINE_HOST"
        myConnection.ConnectionString = connString
        myCommand.Connection = myConnection
        myCommand.CommandText = "test_for_new_document"
        myCommand.CommandType = CommandType.StoredProcedure
        myCommand.Parameters.Add(New OracleParameter("thesource_path", OracleType.VarChar)).Value = SourceFileName
        'myCommand.Parameters("thesource_path").Direction = ParameterDirection.Input
        'myCommand.Parameters("thesource_path").Value = SourceFileName
        myCommand.Parameters.Add(New OracleParameter("the_document_number", OracleType.Number))
        myCommand.Parameters("the_document_number").Direction = ParameterDirection.Output
        myConnection.Open()
        myCommand.ExecuteNonQuery()
        document_id = myCommand.Parameters(1).Value
        myConnection.Close()
       
Any help would be greatly appreciated.

Thanks.