Добавить сортировку пользователей.

***
- Добавил сервис для сортировки пользователей по имени и возрасту.
- Добавил сервис для поиска пользователей по имени.
- Добавил сервис для постраничной навигации по списку пользователей.
***

PhoneStore/Controllers/UsersController.cs

-using System.Linq;
+using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc;
-using PhoneStore.Models;
-using PhoneStore.ViewModels;
+using PhoneStore.Services.Abstractions;
 using Order = PhoneStore.Enums.Order;
 
 namespace PhoneStore.Controllers
 {
     public class UsersController : Controller
     {
-        private readonly MobileContext _db;
+        private readonly IUserService _userService;
 
-        public UsersController(MobileContext db)
+        public UsersController(IUserService userService)
         {
-            _db = db;
+            _userService = userService;
         }
 
         [HttpGet]
-        public IActionResult Index(
-            string filteringCriterionByName, 
-            int page = 1, 
-            Order order = Order.NameAsc)
+        public async Task<IActionResult> Index(string filterByName, Order order = Order.AgeAsc, int page = 1)
         {
             int pageSize = 2;
-            IQueryable<User> users  = _db.Users.AsQueryable();
-            if (!string.IsNullOrEmpty(filteringCriterionByName))
-                users = users.Where(u => u.Name.Contains(filteringCriterionByName));
-            int count = users.Count();
-            
-            users = _db
-                .Users
-                .OrderBy(u => u.Name)
-                .Skip((page - 1) * pageSize)
-                .Take(pageSize);
             ViewBag.NameSort = order == Order.NameAsc ? Order.NameDesc : Order.NameAsc;
             ViewBag.AgeSort = order == Order.AgeAsc ? Order.AgeDesc : Order.AgeAsc;
-            
-            
-            
-            switch (order)
-            {
-                case Order.AgeDesc:
-                    users = users.OrderByDescending(u => u.Age);
-                    break;
-                case Order.AgeAsc:
-                    users = users.OrderBy(u => u.Age);
-                    break;
-                case Order.NameDesc:
-                    users = users.OrderByDescending(u => u.Name);
-                    break;
-                default:
-                    users = users.OrderBy(u => u.Name);
-                    break;
-            }
-
-            UsersViewModel model = new UsersViewModel
-            {
-                Filter = filteringCriterionByName,
-                Users = users.ToArray(),
-                PageViewModel = new PageViewModel(page, count, pageSize )
-            };
+            var model = await _userService.GetAll(order, filterByName, pageSize, page);
             
             return View(model);
         }

PhoneStore/Helpers/UserHelper.cs

+using System.Linq;
+using PhoneStore.Models;
+using PhoneStore.ViewModels;
+
+namespace PhoneStore.Helpers
+{
+    public static class UserHelper
+    {
+        public static UsersViewModel MapToUsersViewModel(
+            this IQueryable<User> self, 
+            string filter, 
+            int page, 
+            int count,
+            int pageSize)
+        {
+            return new UsersViewModel
+            {
+                Users = self.ToArray(),
+                Filter = filter,
+                PageViewModel = new PageViewModel(page, count, pageSize)
+            };
+        }
+    }
+}
\ No newline at end of file

PhoneStore/Services/Abstractions/IPaginationService.cs

+using System.Linq;
+using System.Threading.Tasks;
+using PhoneStore.Models;
+
+namespace PhoneStore.Services.Abstractions
+{
+    public interface IPaginationService
+    {
+        Task<(IQueryable<User>, int)> GetABatchOfData(IQueryable<User> users, int page, int pageSize);
+    }
+}
\ No newline at end of file

PhoneStore/Services/Abstractions/IUserService.cs

+using System.Threading.Tasks;
+using PhoneStore.Enums;
+using PhoneStore.ViewModels;
+
+namespace PhoneStore.Services.Abstractions
+{
+    public interface IUserService
+    {
+        Task<UsersViewModel> GetAll(Order order, string filterByName, int pageSize, int page);
+    }
+}
\ No newline at end of file

PhoneStore/Services/Abstractions/IUsersFilter.cs

+using System.Linq;
+using PhoneStore.Models;
+
+namespace PhoneStore.Services.Abstractions
+{
+    public interface IUsersFilter
+    {
+        IQueryable<User> FilterByName(IQueryable<User> users, string filterByName);
+    }
+}
\ No newline at end of file

PhoneStore/Services/Abstractions/IUsersSortService.cs

+using System.Linq;
+using PhoneStore.Models;
+using Order = PhoneStore.Enums.Order;
+
+namespace PhoneStore.Services.Abstractions
+{
+    public interface IUsersSortService
+    {
+        IQueryable<User> Sort(IQueryable<User> users, Order order);
+    }
+}
\ No newline at end of file

PhoneStore/Services/PaginationService.cs

+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.EntityFrameworkCore;
+using PhoneStore.Models;
+using PhoneStore.Services.Abstractions;
+
+namespace PhoneStore.Services
+{
+    public class PaginationService : IPaginationService
+    {
+        public async Task<(IQueryable<User>, int)> GetABatchOfData(IQueryable<User> users, int page, int pageSize)
+        {
+            int count = await users.CountAsync();
+            return (users.Skip((page - 1) * pageSize).Take(pageSize), count);
+        }
+    }
+}
\ No newline at end of file

PhoneStore/Services/UserService.cs

+
+using System.Linq;
+using System.Threading.Tasks;
+using PhoneStore.Helpers;
+using PhoneStore.Models;
+using PhoneStore.Services.Abstractions;
+using PhoneStore.ViewModels;
+using Order = PhoneStore.Enums.Order;
+
+namespace PhoneStore.Services
+{
+    public class UserService : IUserService
+    {
+        private readonly MobileContext _db;
+        private readonly IUsersSortService _sortService;
+        private readonly IUsersFilter _usersFilter;
+        private readonly IPaginationService _paginationService;
+
+        public UserService(
+            MobileContext db, 
+            IUsersSortService sortService, 
+            IUsersFilter usersFilter, 
+            IPaginationService paginationService)
+        {
+            _db = db;
+            _sortService = sortService;
+            _usersFilter = usersFilter;
+            _paginationService = paginationService;
+        }
+
+        public async Task<UsersViewModel> GetAll(Order order, string filterByName, int pageSize, int page)
+        {
+            var users = _db.Users.AsQueryable();
+            var filteredUsers = _usersFilter.FilterByName(users, filterByName);
+            var sortedUsers = _sortService.Sort(filteredUsers, order);
+            var paginationData = await _paginationService.GetABatchOfData(sortedUsers, page, pageSize);
+            
+            return paginationData.Item1.MapToUsersViewModel(filterByName, page, paginationData.Item2, pageSize);
+        }
+    }
+}
\ No newline at end of file

PhoneStore/Services/UsersFilter.cs

+using System.Linq;
+using PhoneStore.Models;
+using PhoneStore.Services.Abstractions;
+
+namespace PhoneStore.Services
+{
+    public class UsersFilter : IUsersFilter
+    {
+        public IQueryable<User> FilterByName(IQueryable<User> users, string filterByName)
+        {
+            return string.IsNullOrEmpty(filterByName) 
+                ? users 
+                : users.Where(u => u.Name.Contains(filterByName));
+        }
+    }
+}
\ No newline at end of file

PhoneStore/Services/UsersSortService.cs

+using System.Linq;
+using System.Threading.Tasks;
+using PhoneStore.Models;
+using PhoneStore.Services.Abstractions;
+using Order = PhoneStore.Enums.Order;
+
+namespace PhoneStore.Services
+{
+    public class UsersSortService : IUsersSortService
+    {
+        public IQueryable<User> Sort(IQueryable<User> users, Order order)
+        {
+            switch (order)
+            {
+                case Order.AgeDesc:
+                    return users.OrderByDescending(u => u.Age);
+                case Order.AgeAsc:
+                    return users.OrderBy(u => u.Age);
+                case Order.NameDesc:
+                    return users.OrderByDescending(u => u.Name);
+                default: return users.OrderBy(u => u.Name);
+            }
+        }
+    }
+}
\ No newline at end of file

PhoneStore/Startup.cs

@@ -32,6 +32,10 @@ namespace PhoneStore
             services.AddTransient<IDefaultPhoneImagePathProvider>(_ =>
                 new DefaultPhoneImagePathProvider(Configuration["PathToDefaultAvatar:Path"]));
             services.AddTransient<IPhoneService, PhoneService>();
+            services.AddTransient<IUserService, UserService>();
+            services.AddTransient<IUsersSortService, UsersSortService>();
+            services.AddTransient<IUsersFilter, UsersFilter>();
+            services.AddTransient<IPaginationService, PaginationService>();
         }
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.

PhoneStore/Views/Users/Index.cshtml

@@ -16,7 +16,7 @@
                     <input
                         id="name"
                         type="text"
-                        name="filteringCriterionByName" 
+                        name="filterByName"
                         value="@Model.Filter">
                 </label>
                 <input type="text" hidden name="page" value="@Model.PageViewModel.Page">
@@ -33,7 +33,7 @@
                 asp-action="Index"
                 asp-controller="Users"
                 asp-route-order="@ViewBag.NameSort"
-                asp-route-filteringCriterionByName="@Model.Filter">
+                asp-route-filterByName="@Model.Filter">
                 Имя
             </a>
         </th>
@@ -42,7 +42,7 @@
                 asp-action="Index"
                 asp-controller="Users"
                 asp-route-order="@ViewBag.AgeSort"
-                asp-route-filteringCriterionByName="@Model.Filter">
+                asp-route-filterByName="@Model.Filter">
                 Возраст
             </a>
         </th>
@@ -55,18 +55,23 @@
         </tr>
     }
 </table>
-
 @if (Model.PageViewModel.HasPrevious)
 {
-    <a asp-action="Index" asp-controller="Users"
-       asp-route-page="@(Model.PageViewModel.Page - 1)" 
-       asp-route-filteringCriterionByName="@Model.Filter" 
-       class="btn btn-outline-warning">Назад</a>
+    <a
+        asp-action="Index"
+        asp-controller="Users"
+        asp-route-page="@(Model.PageViewModel.Page - 1)" class="btn btn-outline-warning"
+        asp-route-filterByName="@Model.Filter">
+        Назад
+    </a>
 }
 @if (Model.PageViewModel.HasNext)
 {
-    <a asp-action="Index" asp-controller="Users" 
-       asp-route-page="@(Model.PageViewModel.Page + 1)" 
-       asp-route-filteringCriterionByName="@Model.Filter" 
-       class="btn btn-outline-warning">Вперед</a>
+    <a
+        asp-action="Index"
+        asp-controller="Users"
+        asp-route-page="@(Model.PageViewModel.Page + 1)" class="btn btn-outline-warning"
+        asp-route-filterByName="@Model.Filter">
+        Вперед
+    </a>
 }
\ No newline at end of file