Performance problems with combobox and datasource

Question

We have a perfomance problem, when we are connecting a datatable object or something like this to a datasource property of a combobox. Below you find the source code. The SQL-Statement reads about 40000 rows and the result (all 40000) should be listed in the combobox. There is duration about 30 second before this process has finished. Any suggestions?
Dim ds As New DataSet
strSQL = "Select * from am.city"
conn = New Oracle.DataAccess.Client.OracleConnection(Configuration.ConfigurationSettings.AppSettings("conORA"))
comm = New Oracle.DataAccess.Client.OracleCommand(strSQL)
da = New Oracle.DataAccess.Client.OracleDataAdapter(strSQL, conn)
conn.Open()
da.Fill(ds)
conn.Close()
Dim dt As New DataTable
dt = ds.Tables(0)
ComboBox1.DataSource = dt
ComboBox1.ValueMember = dv.Table.Columns("id").ColumnName
ComboBox1.DisplayMember = dv.Table.Columns("city").ColumnName

Answer 1

But how long does it take to fill the DataTable?
I can fill a 40000 row datatable in under 4 seconds.
DataBinding a combo box to that many rows is pretty expensive, and not normally recommended.
David
Dim strConnection As String = "Data Source=oracle;User ID=scott;Password=tiger;"
Dim conn As OracleConnection = New OracleConnection(strConnection)
conn.Open()
Dim cmd As New OracleCommand("select * from (select * from all_objects union all select * from all_objects) where rownum <= 40000", conn)
Dim ds As New DataSet()
Dim da As New OracleDataAdapter(cmd)
Dim begin As Date = Now
da.Fill(ds)
Console.WriteLine(ds.Tables(0).Rows.Count & " rows loaded in " & Now.Subtract(begin).TotalSeconds & " seconds")
outputs
40000 rows loaded in 3.734375 seconds