[NotSupportedException: Collection is read-only.]
   System.Collections.ReadOnlyList.Add(Object obj) +48
   SpringAir.SpecAndQuote.Product.ControlPanel.cmdExSupInclude_Click(Object sender, EventArgs e) in C:\Documents and Settings\Sandro\My Documents\SpringAirRepo\SpecAndQuote\trunk\Product\ProductType\ControlPanel\Controller.cs:728
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +108
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +57
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +18
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
   System.Web.UI.Page.ProcessRequestMain() +1281

IList l = new ArrayList(oldList);
l.Add(item);
obj.list = l;
//... instead of
obj.list.Add(item);