Добавил панель навигации Bootstrap.

PhoneStore/Services/UserService.cs

-
-using System.Linq;
 using System.Threading.Tasks;
 using PhoneStore.Helpers;
 using PhoneStore.Models;

PhoneStore/ViewModels/PageViewModel.cs

@@ -8,10 +8,12 @@ namespace PhoneStore.ViewModels
         public int TotalPages { get; set; }
         public bool HasPrevious => Page > 1;
         public bool HasNext => Page < TotalPages;
+        public int Count { get; set; }
 
         public PageViewModel(int page, int count, int pageSize)
         {
             Page = page;
+            Count = count;
             TotalPages = (int)Math.Ceiling(count / (double)pageSize);
         }
     }

PhoneStore/Views/Users/Index.cshtml

@@ -55,23 +55,29 @@
         </tr>
     }
 </table>
-@if (Model.PageViewModel.HasPrevious)
-{
-    <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)" class="btn btn-outline-warning"
-        asp-route-filterByName="@Model.Filter">
-        Вперед
-    </a>
-}
\ No newline at end of file
+<nav aria-label="Page navigation">
+    <ul class="pagination justify-content-left">
+        @if (Model.PageViewModel.HasPrevious)
+        {
+            <li class="page-item">
+                <a 
+                    asp-action="Index" 
+                    asp-controller="Users" 
+                    class="page-link"
+                    asp-route-page="@(Model.PageViewModel.Page - 1)"
+                    asp-route-filterByName="@Model.Filter">Previous</a>
+            </li>
+        }
+        @if (Model.PageViewModel.HasNext)
+        {
+            <li class="page-item">
+                <a 
+                    class="page-link"
+                     asp-action="Index"
+                    asp-controller="Users"
+                    asp-route-page="@(Model.PageViewModel.Page + 1)" 
+                    asp-route-filterByName="@Model.Filter">Next</a>
+            </li>
+        }
+    </ul>
+</nav>
\ No newline at end of file