I have written the two below methods to auto size the dropdown widths of all the combo boxes on a windows form. However, it doesn’t appear to be hitting any of the combo boxes. When I apply the method ComboBoxDropDownWidth to a single combo box under the form load event it works. To confirm, I also fire ComboBoxAutofitDropDownWidth(this) under the form load event.

public static int ComboBoxDropDownWidth(ComboBox comboBox)
{
    int maxWidth = 0;
    foreach (var obj in comboBox.Items)
    {
        int defaultWidth = TextRenderer.MeasureText(obj.ToString(), comboBox.Font).Width;
        if (defaultWidth > maxWidth)
        {
            maxWidth = defaultWidth;
        }
    }
    return maxWidth;
}

public static void ComboBoxAutofitDropDownWidth(Form form)
{
    var comboBoxes = form.Controls
          .OfType<ComboBox>();

    foreach (var comboBox in comboBoxes)
    {
        comboBox.DropDownWidth = ComboBoxDropDownWidth(comboBox);
    }
}