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How to: Enable Opening ComboBox's Dropdown Window Based on Custom Logic

windowsforms-9507-controls-and-libraries-editors-and-simple-controls-examples-how-to-enable-opening-comboboxs-dropdown-window-based-on-custom-logic.md

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How to: Enable Opening ComboBox's Dropdown Window Based on Custom Logic

  • Oct 25, 2019

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.

csharp
private void comboBoxEdit1_QueryPopUp(object sender, 
  System.ComponentModel.CancelEventArgs e) {
    ComboBoxEdit combo = sender as ComboBoxEdit;
    e.Cancel = combo.Properties.Items.IndexOf(combo.Text) == -1;
}
vb
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