What is the equivalent of Web Forms "Page_Load" in ASP.NET Core 5, so my code will run before any page loading?

Question

Is there a way to execute a code on every page load in ASP.NET Core 5, like there is in Web Forms? In Web Forms I used the Page_Load() event handler, but what is the equivalent in ASP.NET Core 5? So if I call any action in any controller, it will run my code first, then run the action execution.

I found this: How can I execute common code for every request?, But when I tried it I got errors.

Please someone provide me with clear solution.

Also, I need a solution to check the session from one place, instead of writing the "check session code" in each controller, I create the session after the login is succeed, but what is the best way to check the session in all controllers and if it is null then redirect to login page?

Answer 1

In asp.net core, you can use Action filters to replace the "Page_Load" method in webform.

You can register the global scope of Action filters in the startup to ensure that the Action filters will be executed before each action is executed.

Add the following Action filter in your project :

public class MyActionFilter : IActionFilter
    {
        public void OnActionExecuting(ActionExecutingContext context)
        {

                // Do something before the action executes.
            if (!context.HttpContext.Request.Path.ToString().Contains("Login"))
            {
                if (context.HttpContext.Session.GetString("user") == null)
                {
                    context.Result = new RedirectToRouteResult(
                        new RouteValueDictionary { { "controller", "Login" }, { "action", "Index" } });
                }
            }
            
        }

        public void OnActionExecuted(ActionExecutedContext context)
        {
            // Do something after the action executes.
        }
    }

Then in startup.cs ConfigureServices method, add following code to apply it to all scope:

services.AddControllersWithViews(options =>
            {
                options.Filters.Add(typeof(MyActionFilter));
            });