Функция UpdateData() - не работает и возвращает False

Imports System.Data.SqlClient
 
Public Class Author
    Private cnPubs As SqlConnection
    Private daPubs As SqlDataAdapter
    Private dsPubs As DataSet
 
    Public Sub New()
        cnPubs = New SqlConnection()
        cnPubs.ConnectionString = _
            ("Integrated Security=True; Data Source=LocalHost; Initial Catalog=Pubs")
        Dim strSQL As String
        Dim oSelCmd As SqlCommand
        strSQL = "SELECT au_id, au_lname, au_fname FROM authors"
        oSelCmd = New SqlCommand(strSQL, cnPubs)
        daPubs = New SqlDataAdapter()
        daPubs.SelectCommand = oSelCmd
 
        Dim oUpdCmd As SqlCommand
        strSQL = "UPDATE authors set au_lname = @au_lname, au_fname = @au_fname, WHERE au_id = @au_id"
        oUpdCmd = New SqlCommand(strSQL, cnPubs)
        oUpdCmd.Parameters.Add("@au_id", SqlDbType.VarChar, 11, "au_id")
        oUpdCmd.Parameters.Add("@au_lname", SqlDbType.VarChar, 40, "au_lname")
        oUpdCmd.Parameters.Add("@au_fname", SqlDbType.VarChar, 40, "au_fname")
        daPubs.UpdateCommand = oUpdCmd
    End Sub
 
    Public Function GetData() As DataSet
        dsPubs = New DataSet()
        daPubs.Fill(dsPubs, "Authors")
        Return dsPubs
    End Function
 
    Public Function UpdateData(ByVal DSChanged As DataSet) As Boolean
        Try
            daPubs.Update(DSChanged, "Authors")
            Return True
        Catch ex As Exception
            Return False
        End Try
    End Function
End Class