.Net Core Session Management

The Session helps to store user data in the application memory. Since the user data stores on the application it quick and fast to access. .Net Core Session data stored application using the cache, this cache can be either In-Memory or Distributed Cache. 

Session Work-flow:

• On the user request the application from the browser, the server will create a session with an id called Session-Id. 
• This Session-Id will be given to the user in response by storing it in the cookie. So on every next request, this cookie will reach to the application which contains Session-Id. 
• An application uses the SessionId as the main key and stores all user data in the application cache. So by receiving a cookie from a client with Session-Id application will fetch the session stored data as per request. 
• This cookie session is browser-specific it is not sharable between browsers. 
• We can set session time out in our application, where after the time session data will get automatically cleared.

Create A Sample .Net Core MVC Application:

Let's create a sample MVC application to get hands-on for implementing and configuring the session in the application. To create a .Net Core MVC application you can use either Visual Studio 2019(Support .Net Core 3.0 +) or Visual Studio Code. Click here to understand the visual studio code to create a .Net Core Application.

Register Session:

Now register session service in application startup file as follows.

Startup.cs:(Inside of ConfigureService Method)

services.AddSession(options => {
	options.IdleTimeout = TimeSpan.FromMinutes(1);
	options.Cookie.HttpOnly = true;
	options.Cookie.IsEssential = true;
});

IdleTimeout - The IdleTimeout indicates how long the session can be idle before its content is abandoned. Each time session access will reset the timeout. This IdleTimeout only applies to session content on the server, not to the cookie which holds the session-id.

Cookie - The Cookie provides configuration for the cookie used to store the session-id.

Configure Session Middleware:

Now configure the session middleware in the startup file. It should be configured between the middleware like 'app.UseRouting()' and 'app.UseEndpoint()'.

Startup.cs:(Inside of Configure Method):

app.UseRouting();

app.UseSession();

app.UseEndpoints();

Check Session-Id:

We can check the Session-Id value from the 'HttpContext.Session.Id' as follows.

Controllers/TestController.cs:

using Microsoft.AspNetCore.Mvc;
namespace SessionMvc.App.Controllers
{

    [Route("test")]
    public class TestController:Controller
    {
        [HttpGet]
        [Route("get-sessionId")]
        public IActionResult GetSessionId()
        {
            return Content(HttpContext.Session.Id);
        }
    }
}

From the picture above we fetched Session-Id created by the application. But we can observe the session cookie was not created. The reason behind the session cookie not created, the application only stores the session on at least single user data to be stored in the session. So in this case, if the user requested application multiple times, on every request application creates a new session-id, since there was no session cookie.

Store And Fetch Data From Session:

Till now we haven't set and fetch data from the session. So to do that we have some predefined methods to set and fetch session data as follows.

'HttpContext.Session.Set(string key, byte[] value)' - In this, we need to pass one parameter like 'key' which of type string used for fetch stored data, and another parameter of type byte[](byte array) which our actual data to be stored in the session.

'HttpContext.Session.TryGetValue(string key, out byte[] value)' - In this, we need to pass a key-value to fetch the data stored in the session. Here it outputs the value as bytep[](byte array).

Here to save or fetch data we need to deal with a byte array of data. So to make communication easy and simple .Net provide extension method under 'Microsoft.AspNetCore.Http' library.

'HttpContext.Session.SetString(string key, string value)' - In this method both key and value(data to be stored) of type string.

'HttpContext.Session.GetString(string key)' - In this method on passing key, we get session stored data as of type string.

Controllers/TestController.cs:

using Microsoft.AspNetCore.Http;

namespace SessionMvc.App.Controllers
{
    [Route("test")]
    public class TestController : Controller
    {
        [HttpGet]
        [Route("save-to-session")]
        public IActionResult SaveToSession(string name)
        {
            HttpContext.Session.SetString("your_name", name);
            return Content($"{name} save to session");
        }

        [HttpGet]
        [Route("fetch-from-session")]
        public IActionResult FetchFromSession()
        {
            string name = HttpContext.Session.GetString("your_name");
            return Content(name);
        }
    }
}

On saving data to the session, the application adds the session id to cookie and return to the response, so on every next request application uses the session id to fetch the data from the session store until the data expired.

Fetching stored data looks as below.

Store Objects In Session:

Session storage follows the key-value pair dictionary process to save or fetch data. In this process, we have only available methods to store data either in form byte[](byte array) or string, there is no overloaded method to save object or class or entity of data directly into the session.

So to store the Objects in session let's implement custom extension methods as follows.

Utilities/SessionExtenstion.cs:

using System.Text.Json;
using Microsoft.AspNetCore.Http;

namespace SessionMvc.App.Utilities
{
    public static class SessionExtension
    {
        public static void Set<T>(this ISession session, string key, T value)
        {
            session.SetString(key, JsonSerializer.Serialize(value));
        }

        public static T Get<T>(this ISession session, string key)
        {
            var value = session.GetString(key);
            return value == null ? default : JsonSerializer.Deserialize<T>(value);
        }
    }
}

Here we can observe serializing the object to string type and saved it using existing methods like 'ISession.SetString(string key, string value)'.

So to test these extension methods, let's create a model and try to store it in session as follows.

Models/InfoModel.cs:

public class InfoModel
{
	public string Name { get; set; }
	public int Age { get; set; }
	public string Designation { get; set; }
}

Let's update our controller code as follows.

Controllers/TestController.cs:

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using SessionMvc.App.Models;
using SessionMvc.App.Utilities;

namespace SessionMvc.App.Controllers
{

    [Route("test")]
    public class TestController : Controller
    {
        [HttpGet]
        [Route("save-to-session")]
        public IActionResult SaveToSession()
        {
            var info = new InfoModel
            {
                Name = "Naveen",
                Age = 26,
                Designation = ".NET Developer"
            };
            HttpContext.Session.Set<InfoModel>("info", info);
            return Content($"save to session");
        }

        [HttpGet]
        [Route("fetch-from-session")]
        public IActionResult FetchFromSession()
        {
            InfoModel info = HttpContext.Session.Get<InfoModel>("info");
            return Content($"{info.Name} info fetched from session");
        }
    }
}

Clear Session:

'HttpContext.Session.Remove(string key)' - This method removes the given key from the session.

'HttpContext.Session.Clear()' - This method removes the all entries from the session.

Session Using SQL Distributed Cache:

For single-server applications saving session data in-memory of the application will work without any issue. But if an application hosted on multiple servers or nodes using then there is a chance of inconsistency with the application because the in-memory session is specific to the application which runs on a specific server, this in-memory can't be shared between multiple server or nodes.

So it is recommended to use DistributedCache to store the session data. We can use some of the DistributeCache stores like 'Redis', 'SQL Cache', 'NCache', etc. Here we going to use SQL cache to store the session data. Click here to know more about the Distributed SQL Cache, so here I'm going to show code snippet of SQL cache.

Let's install the following nugget to support the .NET Core SQL Cache.

.Net Core CLI Command:
dotnet add package Microsoft.Extensions.Caching.SqlServer

Click here to find the SQL script to generate the cache table.

Now to store the session data in the cache table we need to register SQL distributed service in the startup file.

Startup.cs:

services.AddDistributedSqlServerCache(options => {
	options.ConnectionString = Configuration.GetConnectionString("MyWorldDbConnection");
	options.SchemaName = "dbo";
	options.TableName = "MyCache";
	//options.ExpiredItemsDeletionInterval = TimeSpan.FromMinutes(6);
});

Configure your database connection string in appSettings.json.

That's all the configuration need to set up the SQL cache table and now run the application and check the session store in the cache table as follows.

Wrapping Up:

Hopefully, this article will help to understand the Session Management in .Net Core. I love to have your feedback, suggestions, and better techniques in the comment section.

Follow Me:

Facebook

Twitter

Pinterest