Question

I’m making a combobox “readonly” in this way:

private void comboBox1_SelectedValueChanged(object sender, EventArgs e)
{
     // for this to work, set the comboboxes' Tag to its SelectedIndex after setting that
    ComboBox cb = sender as ComboBox;
     int validSelection = Convert.ToInt32(cb.Tag);
    if (cb.SelectedIndex != validSelection )
    {
        cb.SelectedIndex = validSelection;
    } 
}

…and then trying to set all of the comboboxes on the form to that handler like this:

foreach (Control c in this.Controls)
{
    if (c is ComboBox)
    {
        (c as ComboBox).SelectedValueChanged += comboBox1_SelectedValueChanged;
    }
}

…but the if condition is never equating to true; there are several ComboBoxes on the form…???

Answer 1

The ComboBoxes are most likely inside other panels.

Try going through them recursively:

private void button1_Click(object sender, EventArgs e) {
  ChangeCombos(this);
}

private void ChangeCombos(Control parent) {
  foreach (Control c in parent.Controls) {
    if (c.Controls.Count > 0) {
      ChangeCombos(c);
    } else if (c is ComboBox) {
      (c as ComboBox).SelectedValueChanged += comboBox1_SelectedValueChanged;
    }
  }
}