Similarly add the other methods from the Add a Method drop-down list. After adding all the Methods the BDC Explorer looks like the following one.

In the CustomerService class, replace the code with the following one.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using BdcModel;
 
namespace BdcModel.BdcModel1
{
    public partial class CustomerService
    {
        public static Customer ReadItem(int customerID)
        {
            const string ServerName = @"UKCBEMTSEKIKM01\INSQL01";
            LINQtoSQLDataContext dataContext = new LINQtoSQLDataContext
                  ("Data Source=" + ServerName + ";" +
                   "Initial Catalog=Customer_Details;Integrated Security=True");
            Customer custometer =(from customers in dataContext.Customers.AsEnumerable().Take(20)
                                  where customers.CustomerID == customerID
                                  select customers).Single();
            return custometer;
        }
 
        public static IEnumerable<Customer> ReadList()
        {
            const string ServerName = @"UKCBEMTSEKIKM01\INSQL01";
            LINQtoSQLDataContext dataContext = new LINQtoSQLDataContext
                  ("Data Source=" + ServerName + ";" +
                   "Initial Catalog=Customer_Details;Integrated Security=True");
            IEnumerable<Customer> cust =
        from customers in dataContext.Customers.Take(20)
        select customers;
            return cust;
        }
 
        public static Customer Create(Customer newCustomer)
        {
            const string ServerName = @"UKCBEMTSEKIKM01\INSQL01";
            LINQtoSQLDataContext dataContext = new LINQtoSQLDataContext
                  ("Data Source=" + ServerName + ";" +
                   "Initial Catalog=Customer_Details;Integrated Security=True");
            dataContext.Customers.InsertOnSubmit(newCustomer);
            dataContext.SubmitChanges();
            Customer cust = dataContext.Customers.Single(c => c.CustomerID == newCustomer.CustomerID);
            return cust;
        }
 
        public static void Delete(int customerID)
        {
            const string ServerName = @"UKCBEMTSEKIKM01\INSQL01";
            LINQtoSQLDataContext dataContext = new LINQtoSQLDataContext
                  ("Data Source=" + ServerName + ";" +
                   "Initial Catalog=Customer_Details;Integrated Security=True");
            Customer cust = dataContext.Customers.Single(c => c.CustomerID == customerID);
            dataContext.Customers.DeleteOnSubmit(cust);
            dataContext.SubmitChanges();
 
        }
 
        public static void Update(Customer customer)
        {
            const string ServerName = @"UKCBEMTSEKIKM01\INSQL01";
            LINQtoSQLDataContext dataContext = new LINQtoSQLDataContext
                  ("Data Source=" + ServerName + ";" +
                   "Initial Catalog=Customer_Details;Integrated Security=True");
            Customer cust = dataContext.Customers.Single(c => c.CustomerID == customer.CustomerID);
            cust.CustomerID = customer.CustomerID;
            cust.FirstName = customer.FirstName;
            cust.LastName = customer.LastName;
            dataContext.SubmitChanges();
        }
    }}