1. 确认使用的认证方案是否正确，在 Startup.cs 文件中进行配置：

services.AddAuthentication(options =>
{
    options.DefaultAuthenticateScheme = "Identity.Application";
    options.DefaultChallengeScheme = "Identity.Application";
}).AddCookie("Identity.Application");

2. 在认证成功后更新 AuthenticationStateProvider 中的 UserID，在 Login() 方法中添加以下代码：

var claims = new List
{
    new Claim(ClaimTypes.NameIdentifier, user.Id)
};
var userIdentity = new ClaimsIdentity(claims, "login");
var userPrincipal = new ClaimsPrincipal(userIdentity);

await _httpContextAccessor.HttpContext.SignInAsync(
    CookieAuthenticationDefaults.AuthenticationScheme,
    userPrincipal);

3. 确认 AuthenticationStateProvider 是否正确实现，例如：

public class CustomAuthenticationStateProvider : AuthenticationStateProvider
{
    public override Task GetAuthenticationStateAsync()
    {
        // 获取当前用户的 UserID
        var userId = _httpContextAccessor.HttpContext.User.FindFirstValue(ClaimTypes.NameIdentifier);

        // 如果 UserID 存在，返回已认证的状态
        if (!string.IsNullOrEmpty(userId))
        {
            var claims = new List
            {
                new Claim(ClaimTypes.NameIdentifier, userId)
            };
            var identity = new ClaimsIdentity(claims, "login");
            var principal = new ClaimsPrincipal(identity);
            return Task.FromResult(new AuthenticationState(principal));
        }

        // 如果 UserID 为空，返回未认证的状态
        return Task.FromResult(new AuthenticationState(new ClaimsPrincipal()));
    }
}