Passing TempData with RedirectToAction

Did you configure Session? TempData is using session behind the scenes.

Project.json

"Microsoft.AspNetCore.Session": "1.1.0"

Here is the Startup.cs file. - ConfigureServices method

public void ConfigureServices(IServiceCollection services)
{
     services.AddMemoryCache();
     services.AddSession();
     services.AddMvc();
}

And Configure method.

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
    app.UseSession();
    app.UseMvc(routes => {
        routes.MapRoute(
            name: "default",
            template: "{controller=Home}/{action=Index}/{id?}");
    });
}

Now try with TempData, it will work.

And you can set the environment with set ASPNETCORE_ENVIRONMENT=Development environment variable.

TempData stores data server-side, under user Session. You need to enable sessions (as exception message says). Check this manual.

If you don't want to use sessions - you need some other way to store data (cookies?)

I landed on this question while googling for "asp.net core redirect to action tempdata". I found the answer and am posting it here for posterity.

Problem

My issue was that, after filling in some TempData values and calling RedirectToAction(), TempData would be empty on the page that I was redirecting to.

Solution

Per HamedH's answer here: If you are running ASP.NET Core 2.1, open your Startup.cs file and make sure that in your Configure() method app.UseCookiePolicy(); comes after app.UseMVC();.

Example:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    ...

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

    app.UseCookiePolicy();
}