Session State In ASP.NET Core

{
  "version": "1.0.0-*",
  "buildOptions": {
    "debugType": "portable",
    "emitEntryPoint": true
  },
  "dependencies": {},
  "frameworks": {
    "netcoreapp1.0": {
      "dependencies": {
        "Microsoft.NETCore.App": {
          "type": "platform",
          "version": "1.0.1"
        },
        "Microsoft.AspNetCore.Mvc": "1.0.1",
        "Microsoft.AspNetCore.Server.Kestrel": "1.0.1",
        "Microsoft.AspNetCore.Routing": "1.0.1",
        "Microsoft.AspNetCore.Session": "1.0.1"
      },
      "imports": "dnxcore50"
    }
  }
}

using System;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
namespace WebApplication
{
    public class Startup
    {
        public void Configure(IApplicationBuilder app)
        {
            app.UseSession();
            app.UseMvc();
            app.Run(context =>
            {
                return context.Response.WriteAsync("Hello Readers!");
            });
        }
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
            services.AddSession(options =>
            {
                options.IdleTimeout = TimeSpan.FromMinutes(30);
            });
        }
    }
}

The main reason behind storing bytes array is to make sure that session values are serializable for storage on remote Servers. Apart from int and string, we need to serialize to a byte array to store it in session.

Example

In the example given below, I have set my name into the session in the first request and retrieved the session value in another request.

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
public class HomeController : Controller
{
    [Route("home/index")]
    public IActionResult Index()
    {
        HttpContext.Session.SetString("name", "Jignesh Trivedi");
        return View();
    }
    [Route("home/GetSessionData")]
    public IActionResult GetSessionData()
    {
        ViewBag.data = HttpContext.Session.GetString("name");
        return View();
    }
}

Output

Custom Session Extension methods

As discussed earlier, there are two extension methods to get the data from the session and set the data to the session available, namely GetInt32 and GetString, SetInt32 and SetString. Similarly, we can add our custom extension methods to get and set the value in the session.

In the example given below, I have created an extension method to set a double value to the session and get a double value from the session.

using System;
using Microsoft.AspNetCore.Http;
public static class SessionExtensions
{
    public static double? GetDouble(this ISession session, string key)
    {
        var data = session.Get(key);
        if (data == null)
        {
            return null;
        }
        return BitConverter.ToDouble(data, 0);
    }
    public static void SetDouble(this ISession session, string key, double value)
    {
        session.Set(key, BitConverter.GetBytes(value));
    }
}

Usage of the extension method.

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
public class HomeController : Controller
{
    [Route("home/index")]
    public IActionResult Index()
    {
        HttpContext.Session.SetString("name", "Jignesh Trivedi");
        HttpContext.Session.SetDouble("Percentage", 75.56);
        return View();
    }
    [Route("home/GetSessionData")]
    public IActionResult GetSessionData()
    {
        ViewBag.data = HttpContext.Session.GetString("name");
        ViewBag.Percent = HttpContext.Session.GetDouble("Percentage");
        return View();
    }
}

Output

Store Complex Data in Session

As we are aware, the session is able to store only the byte of an array. Compared to the previous version, ASP.NET Core does not perform any operation such as serialization/ de-serialization on the values stored in the session. Here, I am converting the complex object into JSON and storing it as a string. Later, I retrieve it as a string and de-serialize it to the original object.

Thus, I have written the extension method for setting and getting complex objects to the session.

using System;
using Microsoft.AspNetCore.Http;
using Newtonsoft.Json;
public static class SessionExtensions
{
    public static T GetComplexData<T>(this ISession session, string key)
    {
        var data = session.GetString(key);
        if (data == null)
        {
            return default(T);
        }
        return JsonConvert.DeserializeObject<T>(data);
    }
    public static void SetComplexData(this ISession session, string key, object value)
    {
        session.SetString(key, JsonConvert.SerializeObject(value));
    }
}

Usage of the extension method

In the following example, I have created one public class and within controller action method, created the instance of the class, stored some data, and sent it for storing in session. Similarly, I created one action method to retrieve the complex data from the session.

public class User
{
    public string Name { get; set; }
    public double Percentage { get; set; }
}

Action method

[Route("home/SetComplexData")]
public IActionResult SetComplexData()
{
    User user = new User();
    user.Name = "Jignesh Trivedi";
    user.Percentage = 75.45;    
    HttpContext.Session.SetComplexData("UserData", user);
    return View("index");
}
[Route("home/GetComplexData")]
public IActionResult GetComplexData()
{
    ViewBag.data = HttpContext.Session.GetComplexData<User>("UserData");
    return View();
}

Summary

The main advantage of ASP.NET Core is that it supports modularity. It means that we need to add the module, as we wish to use it in our application. The usage of the session is slightly different than the classic ASP.NET Application. This article helps us to understand how to install, configure, and use sessions with ASP.NET Core.