Web Sevice works perfectly on browser and returns accurate data when invoked. However, when added it to project it doesn't generates the reference .CS file

I have the following Web Service that I run on browser and invoked it. It returns accurate data as XML.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Diagnostics;
using System.Threading;

namespace WebServiceApp
{
    /// <summary>
    /// Summary description for MonthlyBenefitList
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
    [System.Web.Script.Services.ScriptService]
    public class MonthlyBenefitList : System.Web.Services.WebService
    {

        [WebMethod]
        public DataTable GetBenefitMonthlyList(string ListMonth, int ListType)
        {
            var conString = ConfigurationManager.ConnectionStrings["TrackingConnectionString"].ConnectionString;

            using (SqlConnection connection = new SqlConnection(conString))
            {
                connection.Open();

                DataTable DT = new DataTable();


                //string queryString = "SELECT * FROM ExternalEntities WHERE (Type=@Type)";
                string queryString = "SELECT * FROM ExternalEntities";
                SqlCommand BuildCmd = new SqlCommand(queryString, connection);
                BuildCmd.Parameters.Add("@Type", SqlDbType.NVarChar);
                BuildCmd.Parameters["@Type"].Value = "رسمي";
                SqlDataAdapter DtAdapt = new SqlDataAdapter(BuildCmd);
                DtAdapt.Fill(DT);
                DT.TableName = "BenefitMainList";
                return DT;
            }
        }




    }
}

However, As shown in the following picture, When I want to start utilize it in a project and add it through Service Reference, it is added but the .CS file is not generated. So where is the problem and how can I use it without the CS file?

Why is it not generated?