how to read values from the remote OPC Server

Question

I have created one asp.net web service. In this web service I am using the web method as follows. The web service is related to the OPC ( OLE for process control)

public string ReadServerItems(string ServerName) { string txt = ""; ArrayList obj = new ArrayList(); XmlServer Srv = new XmlServer("XDAGW.CS.WCF.Eval.1"); RequestOptions opt = new RequestOptions(); ReadRequestItemList iList = new ReadRequestItemList(); iList.Items = new ReadRequestItem[3]; iList.Items[0] = new ReadRequestItem(); iList.Items[0].ItemName = "ServerInfo.ConnectedClients"; iList.Items[1] = new ReadRequestItem(); iList.Items[1].ItemName = "ServerInfo.TotalGroups"; iList.Items[2] = new ReadRequestItem(); iList.Items[2].ItemName = "EventSources.Area1.Tracking"; ReplyItemList rslt; OPCError[] err; ReplyBase reply = Srv.Read(opt, iList, out rslt, out err);

        if ((rslt == null))
            txt += err[0].Text;
        else
        {

            foreach (xmldanet.xmlda.ItemValue iv in rslt.Items)
            {
                txt += iv.ItemName;
                if (iv.ResultID == null)     // success
                {
                    txt += "   = " + iv.Value.ToString() + "\r\n";
                    obj.Add(txt);
                }
                else
                    txt += " : Error: " + iv.ResultID.Name + "\r\n";
            }

        }

        return txt;
    }

I am using the namespaces as follows

using xmldanet; using xmldanet.xmlda;

I have installed XMLDA.NET client component evaluation. In this there is an in built Test client which successfully reads the values of these data items from the remote OPC server. I also provides the template through which we can build the OPC based applications. In the above code I am trying to read the values of the data items but i am not able to read the values. I have applied the breakpoint. In that I can see that the condition if (iv.ResultID == null) becomes false & also there is null values in the variable rslt. Please tell me where I am doing mistake ? how should I correct my mistake ? can provide me the correct code ?