下面是一个使用Asp.net Core MVC身份验证的代码示例：

1. 首先，在Startup.cs文件中配置身份验证服务。在ConfigureServices方法中添加以下代码：

services.AddAuthentication(options =>
{
    options.DefaultAuthenticateScheme = CookieAuthenticationDefaults.AuthenticationScheme;
    options.DefaultSignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;
    options.DefaultChallengeScheme = CookieAuthenticationDefaults.AuthenticationScheme;
})
.AddCookie(options =>
{
    options.LoginPath = "/Account/Login"; // 设置登录页面的路径
    options.AccessDeniedPath = "/Account/AccessDenied"; // 设置访问被拒绝页面的路径
});

2. 在Configure方法中启用身份验证中间件：

app.UseAuthentication();

3. 创建一个AccountController来处理用户登录和注销的逻辑。在AccountController中添加以下代码：

public class AccountController : Controller
{
    private readonly UserManager _userManager;
    private readonly SignInManager _signInManager;

    public AccountController(UserManager userManager, SignInManager signInManager)
    {
        _userManager = userManager;
        _signInManager = signInManager;
    }

    [HttpGet]
    public IActionResult Login(string returnUrl = null)
    {
        ViewData["ReturnUrl"] = returnUrl;
        return View();
    }

    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task Login(LoginViewModel model, string returnUrl = null)
    {
        ViewData["ReturnUrl"] = returnUrl;
        if (ModelState.IsValid)
        {
            var result = await _signInManager.PasswordSignInAsync(model.Email, model.Password, model.RememberMe, lockoutOnFailure: false);
            if (result.Succeeded)
            {
                return RedirectToLocal(returnUrl);
            }
            else
            {
                ModelState.AddModelError(string.Empty, "Invalid login attempt.");
                return View(model);
            }
        }
        return View(model);
    }

    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task Logout()
    {
        await _signInManager.SignOutAsync();
        return RedirectToAction(nameof(HomeController.Index), "Home");
    }

    private IActionResult RedirectToLocal(string returnUrl)
    {
        if (Url.IsLocalUrl(returnUrl))
        {
            return Redirect(returnUrl);
        }
        else
        {
            return RedirectToAction(nameof(HomeController.Index), "Home");
        }
    }
}

4. 在Views文件夹中创建一个Account文件夹，并在该文件夹下创建Login.cshtml和Logout.cshtml视图。

Login.cshtml视图示例：

@model LoginViewModel
@{
    ViewData["Title"] = "Login";
}

Login

    

        

            
Use a local account to log in.
            

            

            

                
                

                    
                    
                
            
            

                
                

                    
                    
                
            
            

                

                    

                        
                             Remember me
                        
                    
                
            
            

                

                    Log in
                
            
            

                Forgot your password?
            
        
    

Logout.cshtml视图示例：

@{
    ViewData["Title"] = "Logout";
}

Logout