The following code lists a PopupBaseEdit.QueryPopUp event handler which enables opening the dropdown window only if the user typed the text in the edit box which matches an item in the RepositoryItemComboBox.Items collection.
If the user typed a value which does not exist in the collection, the popup is not opened.
private void comboBoxEdit1_QueryPopUp(object sender,
System.ComponentModel.CancelEventArgs e) {
ComboBoxEdit combo = sender as ComboBoxEdit;
e.Cancel = combo.Properties.Items.IndexOf(combo.Text) == -1;
}
Private Sub ComboBoxEdit1_QueryPopUp(ByVal sender As Object, _
ByVal e As System.ComponentModel.CancelEventArgs) _
Handles ComboBoxEdit1.QueryPopUp
Dim combo As ComboBoxEdit = CType(sender, ComboBoxEdit)
If combo.Properties.Items.IndexOf(combo.Text) = -1 Then
e.Cancel = True
End If
End Sub