Session Cookie never set in asp.net core - session

Question

I am trying to configure sessions for an asp.net core 2.0 website, but the session cookie is never set.
I call ..
app.UseSession();
...in Startup.Configure and ...
services.AddDistributedMemoryCache();
services.AddSession(options =>
{
options.IdleTimeout = TimeSpan.FromMinutes(10);
options.Cookie.HttpOnly = false;
options.Cookie.Name = "WS_AUTH_ID";
});
... in the ConfigureServices method.
In the Controller I can acess ...
HttpContext.Session.Id;
... but the id is always different for every request.
Am I missing something?
Update: I should metion that I can set cookies "manually" and the browser will "receive" them.
HttpContext.Response.Cookies.Append("Test_cookie", "yo");

Answer 1

This was the cause for me:
The extension Microsoft.AspNetCore.CookiePolicy (UseCookiePolicy) was blocking the session cookie. Removing this extension and running the app in a new browser window fixed the issue.
Rationale: this extension blocks the cookies sent to the browser until the user accepts them. Since the session key is stored in a cookie and cookies are blocked by this extension... No cookies, no session.
Another workaround could be to enable the application to work without session until the user accepts cookies (I didn't test this workaround).
Hope that helps.

Answer 2

If you have the cookie policy turned ON the session cookiewon't be created until the user accepts the use of Cookies, this is to comply with the EU's GDPR.
You can remove the line
app.UseCookiePolicy();
from you Startup and then it will work, otherwise your users will need to agree to the use of cookies before you can use the cookie for session control.

Answer 3

For me the problem was solved by one of the comments on the question:
The cookie isn't written unless you add something to the session.
So just requesting the Session.Id won't help, you actually have to set something.
In my case it was a variable that was only set after some condition, and before that condition was met, it would create a new session ID over and over again.

Answer 4

You have to type the following in your ConfigureServices method:
services.AddMvc()
.AddSessionStateTempDataProvider();
services.AddDistributedMemoryCache();
services.AddSession(options =>
{
options.IdleTimeout = TimeSpan.FromMinutes(30);
options.Cookie.Name = ".MyApplication";
});
In your Configure type the following
//enable session before MVC
app.UseSession();
app.UseMvc();