Pass TempData between Contollers for Modal return Null?

Question

I want to pass Some String between two controllers to show successful login with modal.I read this topics : ViewBag, ViewData and TempData and RedirectToAction with parameter

but it doesn't work for me and TempData returns Null.it's works fine in this Controllers.

    public async Task<IActionResult> LoginConfirm(LoginViewModel model)
    {
        ApplicationUser user = await userManager.FindByNameAsync(model.Email);
        if (user!=null)
        {
            var status = await signInManager.PasswordSignInAsync(user, model.Pass,model.RememberMe,true);
            if (status.Succeeded)
            {
                TempData["msg"] = "You Login successful ";
                return RedirectToAction("Index","Home");
            }
        }
        TempData["msg"] = "Somethings Wrong!";

        return View("Login");
    }

Answer 1

you have two way

1) when you using the

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;
        });

you enable the GDPR ( General Data Protection Regulation ) And so for as long as the user does not accept your cookie, you will not be able to set cookie in site. And that makes the TempData empty.

2) After Migrating to ASP Core 2.1 I had this issue and after working for a day find the solution:

in Startup.Configure() app.UseCookiePolicy(); should be after app.UseMVC();