private void queryBuilder1_GetDataSourceWidth(QueryBuilder queryBuilder, DataSource datasource, ref int width)
{
    DataSourceControl dsControl = (DataSourceControl) datasource.DSControl.GetControl();
    DataSourceFieldList flControl = dsControl.FieldList;
    Font font = queryBuilder.DiagramObjectFont;
    int maxWidth = 0;
 
    using (Graphics g = CreateGraphics())
    {
        foreach (TextAndObject item in flControl.Items)
        {
            maxWidth = (int) Math.Max(g.MeasureString(item.ToString(), Font).Width, maxWidth);
        }
    }
 
    int extra = 45; // width of checkbox, key mark column and borders
    width = maxWidth + extra;
}