Combo box not refreshed after insert/delete records - vb.net

Question

I am using vb.net and access 2007
I have a problem regarding combo box refresh
This is my code:
Private Sub comboRefresh()
Try
cmbSn_no.DataSource = Nothing
cmbSn_no.Items.Clear()
Dim asql As String = ("SELECT * FROM Vendor_det")
da = New OleDb.OleDbDataAdapter(asql, cnnOLEDB)
da.Fill(ds, "Vendor_det")
cmbSn_no.ValueMember = "sr_no"
cmbSn_no.DataSource = ds.Tables(0)
cmbSn_no.SelectedIndex = 0
'DataGridView1.DataSource = ds.Tables(0)
'DataGridView1.Update()
Catch ex As Exception
MsgBox("ERROR : " & ex.Message.ToString)
End Try
End Sub
Private Sub cmbSn_no_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmbSn_no.SelectedIndexChanged
Dim asql As String = ("SELECT * FROM Vendor_det where sr_no='" & cmbSn_no.Text & "'")
cnnOLEDB.Open()
cmd = New OleDb.OleDbCommand(asql, cnnOLEDB)
dr = cmd.ExecuteReader
If dr.Read = True Then
cmbSn_no.Text = dr("sr_no")
txtPart_no.Text = dr("part_no")
..........
End If
cnnOLEDB.Close()
End Sub
And i call comborefresh() method from add and delete record button click events.
if i dont use the commented code and click on add / delete button then the output comes some how like this:
records in db:
abcd123
bbbc123
if i add a record cccc123.. it should update and my combo box should fill with following records:
abcd123
bbbc123
cccc123
but it fills with
abcd123
bbbc123
cccc123
abcd123
bbbc123
and if i use the commented line then the combo box is filled with "System.Data.DataRowView"
No prompted error comes but i am not getting my answer...
even i have tried with....
combobox.refresh()
combobox.selectedindex=-1
and
combobox.items.clear()
it does not work
Please resolve my problem....
Thank you in advance...:)

Answer 1

Your code to refresh the ComboBox should be OK, but no need to call cmbSn_no.Items.Clear() since cmbSn_no.DataSource = Nothing will remove all data from the ComboBox.
However, based on your code I assume that you declare your DataSet (ds) as form variable, thus when you want to fill in the ds, the old data (first 2 data - abcd123 bbbc123) is still there, and then run the Fill method will add those old data with a whole set of new data - that are abcd123 bbbc123 cccc123. To make sure, try to add this code after da.Fill(ds, "Vendor_det"):
MsgBox.Show(ds.Tables(0).Rows.Count)
I think it will show 5, not 3. If that's the case, try to refresh the DataSet first before Fill, either by creating a new instance of DataSet, or delete the table.