External Web services calling In Navision

I have created a Simple Hello Word Web service on ASP.net and wanted to consume this Web service in Navision.
When I am calling this web service from Navision I am getting "root element is missing" Error.

Microsoft Dynamics NAV

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A call to System.Xml.XmlDocument.Load failed with this message: Data at the root level is invalid. Line 1, position 1.

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OK

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I have written this code.

Url :='http://localhost:55172/WebService.asmx';
reqText := '' + 'HelloWorld' +
'';

// save request text in instream
TempBlob."Primary Key" := 1;
TempBlob.Blob.CREATEOUTSTREAM(ReqBodyOutStream);
ReqBodyOutStream.WRITE(reqText);
TempBlob.Blob.CREATEINSTREAM(ReqBodyInStream);



// run the WebServReqMgt functions to send the request
WebServReqMgt.SetGlobals(ReqBodyInStream,Url,Username,Password);
WebServReqMgt.DisableHttpsCheck;
WebServReqMgt.RUN;

// get the response
WebServReqMgt.SendRequestToWebService();

WebServReqMgt.GetResponseContent(RespBodyInStream);
ResponseXmlDoc := ResponseXmlDoc.XmlDocument;
ResponseXmlDoc.Load(RespBodyInStream);
MESSAGE(ResponseXmlDoc.InnerXml);
END;