用DELPHI7建WEB SERVICE时，服务器端编译成功，但客户端调用出错解决方法

用DELPHI7建WEB SERVICE时，服务器端编译成功，但客户端调用出错
问题：
在服务端如果设置返回给客户端的值为定量时，客户端能够正确调用，但是如果服务端要通过查询数据库
时，客户端就会报错：Access violation at Address 019B8C6C in module "XXWEBSERVICE.dll".Read of Address 000000AC.
 
下面是服务器端WEB MODULE的源代码：

Delphi(Pascal) code

{ SOAP WebModule }unit uWebModule;interfaceuses  SysUtils, Classes, HTTPApp, WSDLPub, SOAPPasInv, SOAPHTTPPasInv,  SOAPHTTPDisp, WebBrokerSOAP, DB, DBClient, MConnect, SConnect, ObjBrkr,  InvokeRegistry, WSDLIntf, TypInfo, WebServExp, WSDLBind, XMLSchema, ADODB,  DBTables;type  TWebModule1 = class(TWebModule)    HTTPSoapDispatcher1: THTTPSoapDispatcher;    HTTPSoapPascalInvoker1: THTTPSoapPascalInvoker;    WSDLHTMLPublish1: TWSDLHTMLPublish;    ADOQuery1: TADOQuery;    ADOStoredProc1: TADOStoredProc;  private    { Private declarations }  public    { Public declarations }  end;var  WebModule1: TWebModule1;implementation{$R *.dfm}uses WebReq,DataType,ServicesInterface;typeTInfo=class(TInvokableClass,IsfcInfo)ProtectedFunction ApproveTestStart(dutSN,OpeID,LineName:string):TsfcInfo;StdCall;End; //定义这个接口类procedure createinfo(out obj:tobject);//此过程为创建类实例，必须手工添加beginobj:=TInfo.Create;//创建类实例end;Function TInfo.ApproveTestStart(dutSN,OpeID,LineName:string):TsfcInfo;StdCall;Begin     Result:=TsfcInfo.Create;     try         with  WebModule1.ADOQuery1 do Begin             close;//[color=#FF0000]测试时发现到这部分就出错了[/color]                          sql.Text:='select emp_name from sajet.sys_emp where rownum=1';             open;             IF NOT ISEMPTY THEN                result.Approved:=fieldbyname('emp_name').AsString;          End;     finally     End;End;initializationWebRequestHandler.WebModuleClass:=TWebModule1;InvRegistry.RegisterInvokableClass(TInfo,createinfo);end.

Delphi(Pascal) code

uses IsfcInfo1;procedure TForm1.Button1Click(Sender: TObject);var    test:TsfcInfo;//定义对象begin     test:=TsfcInfo.Create;     test:=(Httprio1 as IsfcInfo).ApproveTestStart(edit1.Text,'','');      showmessage(test.Approved);//调用方法end;