可以使用令牌端点中的_refresh_token_来更新声明。在配置OpenID Connect时，需要在OnTokenValidated事件中手动请求并使用刷新令牌获取新的声明。

示例代码如下：

services.AddAuthentication(options =>
{
    options.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
    options.DefaultChallengeScheme = OpenIdConnectDefaults.AuthenticationScheme;
})
.AddCookie(options =>
{
    options.ForwardAuthenticate = OpenIdConnectDefaults.AuthenticationScheme;
    options.ForwardSignIn = OpenIdConnectDefaults.AuthenticationScheme;
})
.AddOpenIdConnect(options =>
{
    options.ClientId = Configuration["OpenIdConnect:ClientId"];
    options.ClientSecret = Configuration["OpenIdConnect:ClientSecret"];
    options.Authority = Configuration["OpenIdConnect:Authority"];
    options.CallbackPath = new PathString("/auth/signin-callback");

    // Request refresh token
    options.ResponseType = "code id_token token";
    options.Scope.Clear();
    options.Scope.Add("openid");
    options.Scope.Add("profile");
    options.Scope.Add("email");
    options.Scope.Add("offline_access");

    options.SaveTokens = true;
    options.GetClaimsFromUserInfoEndpoint = true;
    options.Events = new OpenIdConnectEvents
    {
        OnTokenValidated = async ctx =>
        {
            var refreshToken = ctx.TokenEndpointResponse.RefreshToken;
            if (refreshToken != null)
            {
                var newClaims = new List
                {
                    new Claim("newClaimType", "newClaimValue")
                };
                var appOptions = ctx.HttpContext.RequestServices.GetRequiredService>().Value;
                var tokenClient = new TokenClient(appOptions.TokenEndpoint, appOptions.ClientId, appOptions.ClientSecret);
                var tokenResult = await tokenClient.RequestRefreshTokenAsync(refreshToken);

                if (tokenResult.IsError)
                {
                    throw new Exception(tokenResult.Error);
                }

                foreach (var claim in tokenResult.Claims)
                {
                    newClaims.Add(new Claim(claim.Type, claim.Value));
                }

                var identity = ctx.Principal.Identity as ClaimsIdentity;
                identity?.AddClaims(newClaims);
            }
        }
    };
});

注：在请求刷新令牌时，需要在OpenID Connect配置中设置options.ResponseType = "code id_token token"以请求令牌响应中包含刷新令牌。