Error processing web request: Status code 500

Hi, I'm trying to call a simple "Hello World" method in a .NET web service from a script in my Unity project.

On running the Unity application in the editor, it makes it to the point of calling service.HelloWorld() and then I receive the following error:

WebException: There was an error on processing web request: Status code 500(InternalServerError): Internal Server Error System.ServiceModel.Channels.HttpRequestChannel+HttpChannelRequestAsyncResult.WaitEnd ()

The script code is as follows:

     using UnityEngine;
     using System;
     using System.ServiceModel;
     using System.Collections;
     
     public class clsWebServiceTest : MonoBehaviour
     {
         // Use this for initialization
         void Start ()
         {
             MyWebServiceSoapClient service = new MyWebServiceSoapClient(new BasicHttpBinding(),             
             new EndpointAddress("http://localhost:57937/MyWebService.asmx"));
     
             service.Open();
             Debug.Log ("State: " + service.State);
             Debug.Log ("Endpoint: " + service.Endpoint);
             Debug.Log ("Type: " + service.GetType());
             Debug.Log ("Inner Channel: " + service.InnerChannel);
     
             string hello = service.HelloWorld();
     
             Debug.Log(hello);
     
             service.Close();
         }
     }
 

This is my web service code:

 Imports System.Web.Services
 Imports System.Web.Services.Protocols
 Imports System.ComponentModel
 
 ' To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line.
 ' <System.Web.Script.Services.ScriptService()> _
 <System.Web.Services.WebService(Namespace:="http://tempuri.org/")> _
 <System.Web.Services.WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _
 <ToolboxItem(False)> _
 Public Class MyWebService
     Inherits System.Web.Services.WebService
 
     <WebMethod()> _
     Public Function HelloWorld() As String
        Return "Hello World"
     End Function
 
 End Class

And finally, the web.config for the service

 <?xml version="1.0" encoding="utf-8"?>
 <!--
   For more information on how to configure your ASP.NET application, please visit
   http://go.microsoft.com/fwlink/?LinkId=169433
   -->
 <configuration>
   <system.web>
     <compilation debug="true" strict="false" explicit="true" targetFramework="4.5" />
     <httpRuntime targetFramework="4.5" />
   </system.web>
 </configuration>