<%@ ServiceHost Language="C#" Debug="true" Service="Terrasoft.WebApp.ServiceModel.UsrService" CodeBehind="UsrService.svc.cs" %>

  <appSettings>
    ...
    <add key="AllowedLocations" value="...;ServiceModel/UsrService.svc"/>
   ...
  </appSettings>
 
  ...
 
  <location path="ServiceModel/UsrService.svc">
    <system.web>
      <authorization>
        <allow users="*" />
      </authorization>
    </system.web>
  </location>
   ...

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Web;
using System.Text;
 
namespace SimpleCustomService
{
    [ServiceContract]
    public interface UsrIService
    {
        [OperationContract]
        string SPMClientInfo();
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Web;
using System.Text;
 
namespace SimpleCustomService
{
    public class UsrService : UsrIService
    {
        public string SPMClientInfo()
        {
            return "test string";
        }
    }
}

...
 	<service behaviorConfiguration="BaseServiceBehavior" name="SimpleCustomService.UsrService">
        	<endpoint name="UsrServiceEndPoint"
           		binding="webHttpBinding"
           		behaviorConfiguration="RestServiceBehavior"
           		bindingNamespace="http://Terrasoft.WebApp.ServiceModel"
           		contract="SimpleCustomService.UsrIService" />
	        <endpoint address="soap" binding="basicHttpBinding" contract="SimpleCustomService.UsrIService"/>
	        <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
    	</service>
...

http://localhost:8080/NuiLogin.aspx?ReturnUrl=%2f0%2fServiceModel%2fSimpleCustomService.svc