DetermineDropDownWidth

# Code taken from:
# https://stackoverflow.com/questions/4448509/how-to-make-the-combobox-drop-down-list-resize-itself-to-fit-the-largest-item/4811033#4811033
#
# With minor edits
# - to take into account the with of the groupname
# - Width +35 instead of +15, gives better results
#
# NOT yet tested with items names > group names. Due to the indent of the group name, an additional static value might need to be added.

#GroupedComboBox.cs
    private void DetermineDropDownWidth()
    {

        int widestStringInPixels = 0;
        foreach (Object o in Items)
        {
            string toCheckGrp = null;
            string toCheck;
            PropertyInfo pinfo;
            Type objectType = o.GetType();
            if (this.DisplayMember.CompareTo("") == 0)
            {
                toCheck = o.ToString();
            }
            else
            {
                pinfo = objectType.GetProperty(this.DisplayMember);
                toCheck = pinfo.GetValue(o, null).ToString();

                pinfo = objectType.GetProperty(this.GroupMember);
                toCheckGrp = pinfo.GetValue(o, null).ToString();
            }
            if (TextRenderer.MeasureText(toCheck, this.Font).Width > widestStringInPixels)
                widestStringInPixels = TextRenderer.MeasureText(toCheck, this.Font).Width;
            Font grpFont = new Font(Font,FontStyle.Bold);
            if (TextRenderer.MeasureText(toCheckGrp, this.Font).Width > widestStringInPixels)
                widestStringInPixels = TextRenderer.MeasureText(toCheckGrp, grpFont).Width;
        }
        this.DropDownWidth = widestStringInPixels + 35;

# GroupedComboBox.cs
# Needs to be called when setting DataSource
            if (value != null)
            {
                // wrap the object in a binding source and listen for changes
                ...
                DetermineDropDownWidth();
            }
            else
            ...