Add protected admin scope with login

RazorPagesMovie/Pages/Admin/Index.cshtml

@@ -0,0 +1,11 @@
+@page
+@model RazorPagesMovie.Pages.Admin.IndexModel
+@{
+    ViewData["Title"] = "Admin";
+}
+
+<h1>Welcome, @User.Identity?.Name</h1>
+
+<form method="post" asp-page-handler="Logout">
+    <button type="submit" class="btn btn-secondary">Logout</button>
+</form>

RazorPagesMovie/Pages/Admin/Index.cshtml.cs

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+using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Authentication.Cookies;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+
+namespace RazorPagesMovie.Pages.Admin;
+
+public class IndexModel : PageModel
+{
+    public void OnGet()
+    {
+    }
+
+    public async Task<IActionResult> OnPostLogoutAsync()
+    {
+        await HttpContext.SignOutAsync(CookieAuthenticationDefaults.AuthenticationScheme);
+        return RedirectToPage("/Login");
+    }
+}

RazorPagesMovie/Pages/Login.cshtml

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+@page
+@model RazorPagesMovie.Pages.LoginModel
+@{
+    ViewData["Title"] = "Login";
+}
+
+<div class="row justify-content-center">
+    <div class="col-md-4">
+        <h1>Admin Login</h1>
+
+        @if (!string.IsNullOrEmpty(Model.ErrorMessage))
+        {
+            <div class="alert alert-danger">@Model.ErrorMessage</div>
+        }
+
+        <form method="post">
+            <div class="mb-3">
+                <label asp-for="Username" class="form-label"></label>
+                <input asp-for="Username" class="form-control" autofocus />
+            </div>
+            <div class="mb-3">
+                <label asp-for="Password" class="form-label"></label>
+                <input asp-for="Password" type="password" class="form-control" />
+            </div>
+            <button type="submit" class="btn btn-primary">Login</button>
+        </form>
+    </div>
+</div>

RazorPagesMovie/Pages/Login.cshtml.cs

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+using System.Security.Claims;
+using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Authentication.Cookies;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+using Microsoft.EntityFrameworkCore;
+using RazorPagesMovie.Data;
+using RazorPagesMovie.Models;
+
+namespace RazorPagesMovie.Pages;
+
+public class LoginModel : PageModel
+{
+    private readonly RazorPagesMovieContext _context;
+
+    public LoginModel(RazorPagesMovieContext context)
+    {
+        _context = context;
+    }
+
+    [BindProperty]
+    public string Username { get; set; } = string.Empty;
+
+    [BindProperty]
+    public string Password { get; set; } = string.Empty;
+
+    public string? ErrorMessage { get; set; }
+
+    public void OnGet()
+    {
+    }
+
+    public async Task<IActionResult> OnPostAsync(string? returnUrl)
+    {
+        var user = await _context.AdminUser.SingleOrDefaultAsync(u => u.Username == Username);
+        var hasher = new PasswordHasher<AdminUser>();
+
+        if (user is null || hasher.VerifyHashedPassword(user, user.PasswordHash, Password) == PasswordVerificationResult.Failed)
+        {
+            ErrorMessage = "Benutzername oder Passwort ist falsch.";
+            return Page();
+        }
+
+        var identity = new ClaimsIdentity(
+            new[] { new Claim(ClaimTypes.Name, user.Username) },
+            CookieAuthenticationDefaults.AuthenticationScheme);
+
+        await HttpContext.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, new ClaimsPrincipal(identity));
+
+        return LocalRedirect(returnUrl ?? "/Admin");
+    }
+}