Wrong with Consume a Web Service in a Server Method

I want  to Consume a Web Service in a Server Method .

I have created a Proxy DLL that represents the connection to the remote server
, installed  the Proxy into the Innovator Server code tree
,and  declared the Proxy’s name space within Innovator Method
or so created an instance of the Proxy inside a specific server method,  and transfer data.

But When I applying  the method ,it provoids wrongs:

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"><SOAP-ENV:Body><SOAP-ENV:Fault xmlns:af="http://www.aras.com/InnovatorFault"><faultcode>SOAP-ENV:Server</faultcode>

<detail><af:legacy_detail>

The server was unable to process the request.Object reference not set to an object instance

</af:legacy_detail>

<af:exception message="

The server was unable to process the request.Object reference not set to an object instance" type="System.Web.Services.Protocols.SoapException" />

</detail></SOAP-ENV:Fault>

</SOAP-ENV:Body>

</SOAP-ENV:Envelope> 

My code is as follow:

       EDIService ed = new EDIService();  ---> my web service
     
  
      DataSet ds = ed.GetDataInfo("iTEC_MES"," MaterialStock", "11", "MCH000001MSAA", "F11", "", "", "", "IfxByFormNo");   

  // when  debuge here  it coms out wrong!  
            
       int count= ds.Tables[0].Rows.Count ;

Strangly, when  I  apply method in Visual Studio. It works well.

Please help me ! Thanks regard!