Concurrency violation: the UpdateCommand affected 0 of the expected 1 records

[malatesh kumar]

Hi
I am working on vb.net.
I am facing problem when i update the record which i changed in the Textbox on the runtime.

My Code as follows:

 Private Sub btnPersonalcontact_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPersonalcontact.Click

        Dim contact As dbContactsDataSet.tblContactsRow
        contact = DbContactsDataSet.tblContacts.NewtblContactsRow
        With contact

            .ContactMedium = Me.cmbpersonal1.Text
            .ContactNumber = Me.txtperson1.Text
            .IDType = Me.duppersonal1.Text

        End With

        For i = 0 To DbContactsDataSet.tblContacts.Rows.Count - 1
            If Me.txtperson1.Text = DbContactsDataSet.tblContacts.Rows(i).Item(2) Then
                If Not Me.cmbpersonal1.Text = DbContactsDataSet.tblContacts.Rows(i).Item(1) Then
                    DbContactsDataSet.tblContacts.Rows(i).Item(1) = Me.cmbpersonal1.Text

                    MsgBox("Record Updated")

                    GoTo 2

                End If
                MsgBox("Sorry Contact already saved !!")
                Exit Sub
            Else
                GoTo 1
            End If
1:      Next i
        DbContactsDataSet.tblContacts.Rows.Add(contact)
2:      DbContactsDataSet.EndInit()
        TblContactsTableAdapter.Update(DbContactsDataSet.tblContacts)      
      Me.TableAdapterManager.UpdateAll(DbContactsDataSet)
        MsgBox("Contact Saved")
 End Sub

Please solve this......
I am not understanding what is that error??
"Concurrency violation: the UpdateCommand affected 0 of the expected 1 records"