IdentityServer 4外部注销不起作用

Question

我尝试使identityServer4外部注销功能正常工作。但是有一个错误我无法解决（登录工作很棒）。如果我在注销时点击我的SPA（隐式流），它会重定向到注销端点（idsvr4）但是我收到一个错误： NullReferenceException：未将对象引用设置为对象的实例。

在此行的accountController注销功能中：await _persistedGrantService.RemoveAllGrantsAsync(subjectId, "xxx");

并且该行：return await Logout(new LogoutViewModel { LogoutId = logoutId });

这是我的AccountController注销功能：

/// <summary>
    /// Show logout page
    /// </summary>
    [HttpGet]
    [AllowAnonymous]
    public async Task<IActionResult> Logout(string logoutId)
    {
        if ( User.Identity.IsAuthenticated == false)
        {
            // if the user is not authenticated, then just show logged out page
            return await Logout(new LogoutViewModel { LogoutId = logoutId });
        }

    var context = await _interaction.GetLogoutContextAsync(logoutId);
    if (context?.ShowSignoutPrompt == false)
    {
        // it´s safe to automatically sign-out
        return await Logout(new LogoutViewModel { LogoutId = logoutId });
    }

    // show the loutout promp. this presents attacks where the user
    // is automatically signed out by another malicius web page

    var vm = new LogoutViewModel
    {
        LogoutId = logoutId
    };

    return View(vm);

}

//
// POST: /Account/Logout
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Logout(LogoutViewModel model)
{
    var idp = User?.FindFirst(JwtClaimTypes.IdentityProvider)?.Value;
    var subjectId = HttpContext.User.Identity.GetSubjectId();


    if ( idp != null && idp != IdentityServerConstants.LocalIdentityProvider)
    {
        if (model.LogoutId == null)
        {
            model.LogoutId = await _interaction.CreateLogoutContextAsync();
        }
        string url = "/Account/Logout?logoutId=" + model.LogoutId;
        try
        {
            await HttpContext.Authentication.SignOutAsync(idp, new AuthenticationProperties { RedirectUri = url });

        }
        catch(NotSupportedException)
        {
        }
    }

    // delete authentication cockie
    await _signInManager.SignOutAsync();

    // set this so UI rendering sees an anonymous user
    HttpContext.User = new ClaimsPrincipal(new ClaimsIdentity());

    // get context information (client name, post logout redirect uri and iframe for federated signout)
    var logout = await _interaction.GetLogoutContextAsync(model.LogoutId);

    var vm = new LoggedOutViewModel
    {
        PostLogoutRedirectUri = logout?.PostLogoutRedirectUri,
        ClientName = logout?.ClientId,
        SignOutIframeUrl = logout?.SignOutIFrameUrl
    };

    await _persistedGrantService.RemoveAllGrantsAsync(subjectId, "xxx");

    return Redirect("localhost:5000/index.html");
    // return View("LoggedOut", vm);
}

带身份验证的Staartup.cs

public void ConfigureServices(IServiceCollection services)
        {
            //services.ConfigureDapperConnectionProvider<SqlServerConnectionProvider>(Configuration.GetSection("DapperIdentity"))
            //        .ConfigureDapperIdentityCryptography(Configuration.GetSection("DapperIdentityCryptography"))
            //        .ConfigureDapperIdentityOptions(new DapperIdentityOptions { UseTransactionalBehavior = false }); //Change to True to use Transactions in all operations

            services.ConfigureDapperConnectionProvider<MySqlConnectionProvider>(Configuration.GetSection("DapperIdentity"))
                    .ConfigureDapperIdentityCryptography(Configuration.GetSection("DapperIdentityCryptography"))
                    .ConfigureDapperIdentityOptions(new DapperIdentityOptions { UseTransactionalBehavior = false }); //Change to True to use Transactions in all operations

           // services.ConfigureDapperConnectionProvider<PostgreSqlConnectionProvider>(Configuration.GetSection("DapperIdentity"))
            //        .ConfigureDapperIdentityCryptography(Configuration.GetSection("DapperIdentityCryptography"))
            //        .ConfigureDapperIdentityOptions(new DapperIdentityOptions { UseTransactionalBehavior = false }); //Change to True to use Transactions in all operations

            services.AddIdentity<CustomUser, CustomRole>(x =>
                                                         {
                                                             x.Password.RequireDigit = false;
                                                             x.Password.RequiredLength = 1;
                                                             x.Password.RequireLowercase = false;
                                                             x.Password.RequireNonAlphanumeric = false;
                                                             x.Password.RequireUppercase = false;
                                                         })
                   // .AddDapperIdentityFor<PostgreSqlConfiguration>()
                    //.AddDapperIdentityFor<SqlServerConfiguration>()
                    .AddDapperIdentityFor<MySqlConfiguration>()
                    .AddDefaultTokenProviders();

            services.AddMvc();

            // Add application services.
            services.AddTransient<IEmailSender, AuthMessageSender>();
            services.AddTransient<ISmsSender, AuthMessageSender>();

            services.AddIdentityServer()
                    .AddDeveloperSigningCredential()
                    .AddInMemoryPersistedGrants()
                    .AddInMemoryIdentityResources(Config.GetIdentityResources())
                    .AddInMemoryApiResources(Config.GetApiResources())
                    .AddInMemoryClients(Config.GetClients())
                    .AddAspNetIdentity<CustomUser>()
                    .AddProfileService<ProfileService>();

            services.AddAuthentication(IdentityServerAuthenticationDefaults.AuthenticationScheme)
                .AddIdentityServerAuthentication(options =>
               {
                   options.Authority = "http://localhost:4200";
                   options.ApiName = "api1";
                   options.SupportedTokens = SupportedTokens.Both;
               });
        }

有谁知道这个错误是什么？

*** **** UPDATE 我自己解决了这个问题