- Вынес создание отзыва в сервис.

PhoneStore/Controllers/FeedbackController.cs

-using System;
-using System.Linq;
-using System.Text.Json;
 using Microsoft.AspNetCore.Identity;
 using Microsoft.AspNetCore.Mvc;
-using Microsoft.EntityFrameworkCore;
 using PhoneStore.Models;
-using PhoneStore.ViewModels;
+using PhoneStore.Services.Interfaces;
 using PhoneStore.ViewModels.Feedback;
 
 namespace PhoneStore.Controllers
 {
     public class FeedbackController : Controller
     {
-        private readonly MobileContext _db;
         private readonly UserManager<User> _userManager;
+        private readonly IFeedbackService _feedbackService;
 
-        public FeedbackController(MobileContext db, UserManager<User> userManager)
+        public FeedbackController(
+            UserManager<User> userManager, 
+            IFeedbackService feedbackService)
         {
-            _db = db;
             _userManager = userManager;
+            _feedbackService = feedbackService;
         }
 
-        // GET
+        [HttpGet]
         public ActionResult<FeedbackViewModel> Create(FeedbackCreateViewModel model)
         {
-            Feedback feedback = new Feedback
-            {
-                CreationDateTime = DateTime.Now,
-                Text = model.Text,
-                PhoneId = model.PhoneId,
-                UserId = int.Parse(_userManager.GetUserId(User))
-            };
-            _db.Feedbacks.Add(feedback);
-            _db.SaveChanges();
-            Feedback newFeedback = _db.Feedbacks
-                .Include(f => f.User)
-                .Include(f => f.Phone)
-                .First(f => f.Id == feedback.Id);
-            FeedbackViewModel feedbackViewModel = new FeedbackViewModel
-            {
-                Id = newFeedback.Id,
-                Text = newFeedback.Text,
-                PhoneId = newFeedback.PhoneId,
-                UserId = newFeedback.UserId,
-                CreationDateTime = newFeedback.CreationDateTime
-            };
+            //TODO: валидация.
+            var userId = int.Parse(_userManager.GetUserId(User));
+            var feedbackViewModel = _feedbackService.Create(model, userId);
+            
             return Json(feedbackViewModel);
         }
     }

PhoneStore/Helpers/FeedbackMapper.cs

+using PhoneStore.Models;
+using PhoneStore.ViewModels.Feedback;
+
+namespace PhoneStore.Helpers
+{
+    public static class FeedbackMapper
+    {
+        public static FeedbackViewModel MapToFeedbackViewModel(this Feedback self)
+        {
+            FeedbackViewModel feedbackViewModel = new FeedbackViewModel
+            {
+                Id = self.Id,
+                Text = self.Text,
+                PhoneId = self.PhoneId,
+                UserId = self.UserId,
+                CreationDateTime = self.CreationDateTime
+            };
+            return feedbackViewModel;
+        }
+    }
+}
\ No newline at end of file

PhoneStore/Services/FeedbackService.cs

+using System;
+using System.Linq;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.EntityFrameworkCore;
+using PhoneStore.Helpers;
+using PhoneStore.Models;
+using PhoneStore.Services.Interfaces;
+using PhoneStore.ViewModels.Feedback;
+
+namespace PhoneStore.Services
+{
+    public class FeedbackService : IFeedbackService
+    {
+        private readonly MobileContext _db;
+        private readonly UserManager<User> _userManager;
+
+        public FeedbackService(
+            MobileContext db, 
+            UserManager<User> userManager)
+        {
+            _db = db;
+            _userManager = userManager;
+        }
+
+        public FeedbackViewModel Create(FeedbackCreateViewModel model, int userId)
+        {
+            Feedback feedback = new Feedback
+            {
+                CreationDateTime = DateTime.Now,
+                Text = model.Text,
+                PhoneId = model.PhoneId,
+                UserId = userId
+            };
+            _db.Feedbacks.Add(feedback);
+            _db.SaveChanges();
+            Feedback newFeedback = _db.Feedbacks
+                .Include(f => f.User)
+                .Include(f => f.Phone)
+                .First(f => f.Id == feedback.Id);
+            FeedbackViewModel feedbackViewModel = newFeedback.MapToFeedbackViewModel();
+            
+            return feedbackViewModel;
+        }
+    }
+}
\ No newline at end of file

PhoneStore/Services/Interfaces/IFeedbackService.cs

+using PhoneStore.ViewModels.Feedback;
+
+namespace PhoneStore.Services.Interfaces
+{
+    public interface IFeedbackService
+    {
+        FeedbackViewModel Create(FeedbackCreateViewModel model, int userId);
+    }
+}
\ No newline at end of file

PhoneStore/Views/Phones/About.cshtml

@@ -21,7 +21,7 @@
                         <label for="text">Добавьте отзыв о телефоне</label>
                         <input type="text" class="form-control" id="text" placeholder="Минимальная длина отзыва 10 символов">
                         <input type="text" hidden name="phoneId" id="@Model.Id">
-                        <button class="my-3" type="submit">Отправить</button>
+                        <button class="my-3 btn btn-outline-warning" type="submit">Отправить</button>
                     </div>
                 </form>
             }

PhoneStore/Views/Shared/_Layout.cshtml

@@ -28,7 +28,7 @@
                         <a class="nav-link text-dark" asp-area="" asp-controller="Brands" asp-action="Create">Добавить бренд</a>
                     </li>
                     <li class="nav-item">
-                        <input type="text" id="search" class="form-control" placeholder="Критерии для поиска">
+                        <input type="text" id="search" class="form-control" placeholder="Критерии для поиска пользователей">
                     </li>
                 </ul>
             </div>