在 localhost 上使用 asp.net core 2.1 身份时，TempData 丢失

Question

Installed new asp.net core 2.1 identity (the one using RCL) to play with it. Scaffolded Login, Registration and Profile pages. Checking profile page:

Areas.Identity.Pages.Account.Manage.Index.cshtml.cs

I came accross this property:

    [TempData]
    public string StatusMessage { get; set; }

which is set when updating profile page:

    StatusMessage = "Your profile has been updated";
    return RedirectToPage();

The funny thing is the message is not shown when running locally. The funnier one is when I publish it to Azure, it works.

My Startup.cs do have config as indicated by ofiical docs:

https://docs.microsoft.com/en-us/aspnet/core/fundamentals/app-state?view=aspnetcore-2.1#tempdata

which goes:

 .AddSessionStateTempDataProvider()

and

 app.UseSession();

Here is the full source code:

https://github.com/kedzior-io/dotnetpwa/tree/model-status-message-is-empty-on-redirect

Any idea what am I missing?

Answer 1

So looks like offical docs are no good:

https://docs.microsoft.com/en-us/aspnet/core/fundamentals/app-state?view=aspnetcore-2.1#tempdata

Docs:

public void ConfigureServices(IServiceCollection services)
{
    services.Configure<CookiePolicyOptions>(options =>
    {
        options.CheckConsentNeeded = context => true;
        options.MinimumSameSitePolicy = SameSiteMode.None;
    });

    services.AddMvc()
        .SetCompatibilityVersion(CompatibilityVersion.Version_2_1)
        .AddSessionStateTempDataProvider();

    services.AddSession();
}

Should be:

public void ConfigureServices(IServiceCollection services)
{
    services.Configure<CookiePolicyOptions>(options =>
    {
        options.CheckConsentNeeded = context => true;
        options.MinimumSameSitePolicy = SameSiteMode.None;
    });

    services.AddSession(); // That should be BEFORE .AddMvc()

    services.AddMvc()
        .SetCompatibilityVersion(CompatibilityVersion.Version_2_1)
        .AddSessionStateTempDataProvider();


}

Thanks @Tony Morris

Answer 2

I'm using aspnet core 2.2, and in my case changing the order as suggested by Artur's answer didn't work.

I solved this by following the official documentation , where it says:

Session state cookies are not essential. Session state isn't functional when tracking is disabled. The following code makes session cookies essential:

services.AddSession(options =>
{
    options.Cookie.IsEssential = true;
});

Having this set solves the issue no matter if it's placed before or after services.AddMvc()

Answer 3

My site's cookie policy meant the TempData cookie was not being saved. So I added code to mark the cookie as "essential":

services.AddControllersWithViews()
    .AddCookieTempDataProvider(t => t.Cookie.IsEssential = true);