CODEWITHSUNDEEP
asp.netasp.net-mvc
Zarif
Zarif

Reputation: 597

How to create an object once and use it several times in Controller

I want to populate an object using methods in a Controller class. So I've created the object in the Controller class and then tried to populate it using methods in the class. This does not work though, because everytime a method in a controller is called, the entire Controller class is reinitiated. So I get a brand new object everytime I try to populate the object. However, I don't know how else I can create an object and populate it. I've added the code below. The object I'm talking about is ProcessModel. Ignore the other objects I created at the top of the class.

Controller:

public class HomeController : Controller
{
    ProcessModel pm = new ProcessModel();
    RetrievePatterns pt = new RetrievePatterns();
    RetrieveModel rm = new RetrieveModel();

    public IActionResult Index()
    {
        FindPatterns fp = new FindPatterns(rm.pm, pt.KpiPatterns);
        ViewData["KPIs"] = fp.passdata;
        return View();
    }

    [HttpPost]
    public IActionResult AddEvent([FromBody] Event data)
    {
        data.ID = pm.EventObjects.Count + 1;
        pm.EventObjects.Add(data);
        return Json(pm.EventObjects.Count);
    }

    [HttpPost]
    public IActionResult AddProcessName(string data)
    {
        pm.ID = 1;
        pm.Name = data;
        return Json(new { title = pm.Name });
    }

    public IActionResult About()
    {
        ViewData["Message"] = "Your application description page.";

        return View();
    }

    public IActionResult Contact()
    {
        ViewData["Message"] = "Your contact page.";

        return View();
    }

    public ActionResult Error()
    {
        return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
    }
}

Object:

public class ProcessModel
{
    public List<Event> EventObjects = new List<Event>();
    public List<Entity> EntityObjects = new List<Entity>();
    public int ID { get; set; }
    public string Name { get; set; }
}

Upvotes: 1

Views: 809

Answers (2)

Emre Kabaoglu
Emre Kabaoglu

Reputation: 13146

You could create a Singleton class which is responsible to create only one instance from Process model;

public class ProcessModelSingleton
{
    private static ProcessModel _processModel = new ProcessModel();

    private ProcessModelSingleton()
    {

    }

    public static ProcessModel Instance
    {
        get { return _processModel; }
    }
}

Then assign it a global variable in the controller;

ProcessModel pm = ProcessModelSingleton.Instance;

EDIT

Created instance by singleton class shared by all users. So, if you want to make it user specific, using Session is the best option.

public ProcessModel pm {
    get
    {
        if (Session["ProcessModel"] == null)
        {
            Session["ProcessModel"] = new ProcessModel();
        }
        return (ProcessModel)Session["ProcessModel"];
    }  
}

Upvotes: 1

K. Wood
K. Wood

Reputation: 29

Keep in mind static variables are shared across all users for that web server. So data populated into a singleton class by one user's request can be read/overwritten by a different user's request. This may be what you are after, but if not you should look into Session State.

ASP.NET Session State Overview

As HTTP is stateless by nature, usage of sessions are discouraged my Microsoft for Asp.NET. By default they are only visible to the web server that creates them so if you are using a farm, you either need to look at server affinity (also called sticky sessions) with a load balancer or out of proc state (such as SQL Server or NCache).

Ideally your application design should avoid the need for sessions and carry only the necessary data between requests via cookies and/or query strings. For more complex applications however this is usually not possible and so Session State is used.

Upvotes: 1

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