Добавил форму входа (Login)

webinar65/Controllers/AccountController.cs

+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.AspNetCore.Mvc;
+using webinar65.Models;
+using webinar65.ViewModels;
+
+namespace webinar65.Controllers
+{
+    public class AccountController : Controller
+    {
+        private UserManager<User> _userManager;
+        private SignInManager<User> _signInManager;
+
+        public AccountController(UserManager<User> userManager, SignInManager<User> signInManager)
+        {
+            _userManager = userManager;
+            _signInManager = signInManager;
+        }
+
+        [HttpGet]
+        public IActionResult Login(string returnUrl)
+        {
+            ViewBag.returnUrl = returnUrl;
+            return View();
+        }
+
+        [HttpPost]
+        public async Task<IActionResult> Login(LoginViewModel model, string returnUrl)
+        {
+            if (ModelState.IsValid)
+            {
+                var user = await _userManager.FindByEmailAsync(model.Email);
+                var result = await _signInManager.PasswordSignInAsync(
+                    user.UserName,
+                    model.Password,
+                    false,
+                    false
+                );
+
+                if (result.Succeeded)
+                    return Redirect(returnUrl ?? "/");
+
+                ModelState.AddModelError(nameof(LoginViewModel.Email), "Invalid email or password");
+            }
+
+            return View(model);
+        }
+    }
+}

webinar65/Controllers/HomeController.cs

-using System;
-using System.Collections.Generic;
-using System.Diagnostics;
-using System.Linq;
-using System.Threading.Tasks;
+using System.Diagnostics;
+using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
 using webinar65.Models;
 
 namespace webinar65.Controllers
 {
+    [Authorize]
     public class HomeController : Controller
     {
         public IActionResult Index()
@@ -40,4 +38,4 @@ namespace webinar65.Controllers
             return View(new ErrorViewModel {RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier});
         }
     }
-}
\ No newline at end of file
+}

webinar65/ViewModels/LoginViewModel.cs

+using System.ComponentModel.DataAnnotations;
+
+namespace webinar65.ViewModels
+{
+    public class LoginViewModel
+    {
+        [Required]
+        [UIHint("email")]
+        public string Email { get; set; }
+
+        [Required]
+        [UIHint("password")]
+        public string Password { get; set; }
+    }
+}

webinar65/Views/Account/Login.cshtml

+@model webinar65.ViewModels.LoginViewModel
+
+@{
+    ViewBag.Title = "Login";
+    Layout = "_Layout";
+}
+
+<h2>Login</h2>
+
+<div asp-validation-summary="All" class="text-danger"></div>
+
+<form asp-action="Login" method="post">
+    <input type="hidden" name="returnUrl" value="@ViewBag.returnUrl"/>
+    <div class="form-group">
+        <label asp-for="Email">Email</label>
+        <input asp-for="Email" class="form-control"/>
+    </div>
+    <div class="form-group">
+        <label asp-for="Password">Password</label>
+        <input asp-for="Password" class="form-control"/>
+    </div>
+
+    <button type="submit" class="btn btn-primary">Login</button>
+</form>