Enterprise Application Architecture with LINQ to SQL

using System;
using System.Linq;
using System.Collections.Generic;
using System.Text;

using Northwind.Service;
using Northwind.Data.DTO;
using Northwind.Business.DataInterfaces;
using Northwind.Presentation.ViewInterfaces;

/*
 **************************************************************
 * Author: Rohit Gadagkar (rohit.gadagkar@gmail.com)
 * Copyright © 2007 Rohit Gadagkar
 * License:
 * Free without any restrictions whatsoever 
 *
 * Created: 9/1/2007
 * 
 * THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY
 * OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT
 * LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE.
 **************************************************************  
*/

namespace Northwind.Presentation
{
    /// <summary>
    /// This presenter is associated with IViewCustomerListing and
    /// implements the functionality for a READ only view of customers.
    /// </summary>
    /// <remarks>
    /// There are two overloads for the constructor. The first overload 
    /// internally creates a default instance of the service. The second overload 
    /// may be used in unit tests by injecting mocked objects as dependencies.
    /// </remarks>
    public class ListCustomersPresenter : BasePresenter<ListCustomersPresenter, Customer>
    {
        protected ICustomerService service;

        public ListCustomersPresenter(IViewCustomerListing view, IDaoFactory daoFactory)
            : base((IView<ListCustomersPresenter,Customer>) view, daoFactory) 
        {
            service = new CustomerService(base.DaoFactory);
        }

        public ListCustomersPresenter(IViewCustomerListing view, 
            IDaoFactory daoFactory, ICustomerService service)
            : base((IView<ListCustomersPresenter, Customer>)view, daoFactory)
        {
            this.service = service;
        }

        //  Override initialize view to display total customer count and pages
        public override void InitializeView()
        {
            base.InitializeView();
            View.TotalCustomers = service.GetCustomersCount();
        }

        public void ShowCurrentPage()
        {
            IEnumerable<Customer> ds = null;
            if (String.IsNullOrEmpty(View.SortPropertyName))
                ds = service.GetCustomersByPage(StartRowIndex, View.PageSize);
            else
            {
                if (String.IsNullOrEmpty(View.PrevSortPropertyName) ||
                    View.SortPropertyName != View.PrevSortPropertyName)
                {
                    View.SortAscending = true;
                    View.PrevSortPropertyName = View.SortPropertyName;
                }
                else if(!View.PageIndexChanged) 
                    View.SortAscending = !View.SortAscending;
                string sortParam = String.Concat(
                    View.SortPropertyName,
                    View.SortAscending ? "" : " DESC");
                ds = service.GetCustomersByPage(StartRowIndex, View.PageSize,
                    sortParam);
            }
            View.DisplayData(ds);
            View.TotalCustomers = service.GetCustomersCount();
        }

        /*
         * Override base implementation in case the presenter needs strongly typed access
         * to the specific view
         */
        protected new IViewCustomerListing View
        {
            get { return (IViewCustomerListing)base.View; }
            set { base.View = (IView<ListCustomersPresenter, Customer>)value; }
        }

        protected int StartRowIndex
        {
            get {
                return View.CurrentPageIndex * View.PageSize;
            }
        }

        protected override IEnumerable<Customer> GetInitialViewData()
        {
            if (View.IsPagingEnabled)            
                return service.GetCustomersByPage(StartRowIndex, View.PageSize);            
            else return service.GetAllCustomers();
        }
    }
}