[VB.NET]Problem mit MySQL

Public Shared Sub abfrage_ausfuehren_start_form(ByVal dieser_sql As String)
        Try
            conn.ConnectionString = myConnectionString
            conn.Open()
            da = New MySqlDataAdapter(dieser_sql, conn)
            Dim dt As New DataTable
            da.Fill(dt) 'FEHLER
            Form1.lb_anzahl.Text = dt.Rows.Count.ToString
            Form1.DataGridView1.DataSource = dt
            conn.Close()
        Catch ex As MySql.Data.MySqlClient.MySqlException
            MessageBox.Show(ex.Message)
        End Try
    End Sub