Session variable value is getting null in ASP.NET Core

Question

I am setting a session variable in one method and trying to get the session variable value from the another method in a controller but its always getting null:

Here is my code:

public class HomeController : Controller
{
    public IActionResult Index()
    { 
        HttpContext.Session.SetString("Test", "Hello!");
        var message = HttpContext.Session.GetString("Test");// Here value is getting correctly
        return View();
    }

    public IActionResult About()
    {
        var message = HttpContext.Session.GetString("Test"); // This value is always getting null here

        return View();
    }
}

Here is my session configuration in Startup class:

In ConfigureServices() method:

services.Configure<CookiePolicyOptions>(options =>
{
    // This lambda determines whether user consent for non-essential cookies is needed for a given request.
    options.CheckConsentNeeded = context => true;
    options.MinimumSameSitePolicy = SameSiteMode.None;
});

services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
services.AddDistributedMemoryCache();
services.AddMvc().AddSessionStateTempDataProvider();
services.AddSession(options =>
{
    options.Cookie.Name = "TanvirArjel.Session";
    options.IdleTimeout = TimeSpan.FromDays(1);
});

In Configure() method:

app.UseSession();
app.UseMvc(routes =>
{
    routes.MapRoute(
        name: "default",
        template: "{controller=Home}/{action=Index}/{id?}");
});

Very strange and peculiar problem! Any help will be highly appreciated!

Melda

Answer 1

For ASP.NET Core 2.1 and 2.2

In the ConfigureServices method of the Startup class, Set options.CheckConsentNeeded = context => false; as follows:

services.Configure<CookiePolicyOptions>(options =>
{
  // This lambda determines whether user consent for non-essential cookies is needed for a given request.
  options.CheckConsentNeeded = context => false;
  options.MinimumSameSitePolicy = SameSiteMode.None;
});

Problem solved!

Melda

Works for me in asp.net Core 2.1 mvc web app! Great Thanks – Outhe

This worked for me. Thank you. Some others suggested adding services.AddMemoryCache() to ConfigureServices and app.UseCookiePolicy() to Configure, but that wasn't necessary. – Infuscate

But doesn't this indicate CheckConsentNeeded is false by default? learn.microsoft.com/en-us/dotnet/api/… – Idellaidelle

As a boolean property default value is false but during the project template generation default value is set to true. – Melda

Not Working for me. Is there anything else which i can do. – Duntson

Check your start up setting please! – Melda

not worked for me to after couple redirections the session ends and I need to login again. – Holiday

that happens only when I use iis as host in my iis express (from vs2017) the session works fine – Holiday

This answer and app.UseSession(); helped me get a hold of session, thanks. – Trista

I think the IsEssential cookie option needs also to be present: services.AddSession(options => { options.Cookie.IsEssential = true; }); – Andreasandree

This is a bad approach. This will make your website/application non-GDPR compliant. Check Max Favilli's answer. This will fix your problem and still prompt the user for consent. – Deck

Answer 2

You can also just set Cookie.IsEssential = true as explained here: https://andrewlock.net/session-state-gdpr-and-non-essential-cookies/

There is an overload of services.AddSession() that allows you to configure SessionOptions in your Startup file. You can change various settings such as session timeout, and you can also customise the session cookie. To mark the cookie as essential, set IsEssential to true:

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

    services.AddSession(opts => 
    {
        opts.Cookie.IsEssential = true; // make the session cookie Essential
    });
    services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
}

Lustig

Im loosing the value between controllers should that happen with the above? – Kincardine

Answer 3

I have had the same issue and tried the following separately and I found that either of them does work for me!

 1. options.CheckConsentNeeded = context => false;
 2. opts.Cookie.IsEssential = true; // make the session cookie Essential

However, not quite sure though, I think #1 might potentially lead to the breach of GDPR. Hence I would prefer #2.

Kneedeep

Answer 4

This might be a front end configuration issue.

The session issue you're experiencing might be due to the configuration of your front-end application. If you're using a separate front-end application (e.g. Angular, React, or Vue.js) to interact with your ASP.NET Core API, make sure the HTTP requests sent to the API include the necessary information for handling sessions (and save cookies in the browser).

If your session is persisted between two requests using Postman or Swagger, this is probably it.

i.e. to fix this on an Angular front-end, you must add this in the HttpClient options of your requests: { withCredentials: true }

Glyn

Answer 5

I tried adding the mentioned lines from Microsoft docs on session it didn't work.

As I see from the code of HttpContext.Session Session can be used in the same request.

So at last, I created one static class as below which helped as Session throughout the application.

public static class SessionHelper
    {
        private static IDictionary<string, string> Session { get; set; } = new Dictionary<string, string>();

        public static void setString(string key, string value)
        {
            Session[key] = value;
        }

        public static string getString(string key)
        {
            return Session.ContainsKey(key) ? Session[key] : string.Empty;
        }
    }

Usage:

set string in one request

SessionHelper.setString("UserId", "123");

read string in another request

SessionHelper.getString("UserId");

Hope it helps!

Jug