Cancel Request after press button

the easiest approach is to have a request id for each page render. a post or ajax call would pass this request id. server side on the request a cancelation token would be added to a static collection keyed by request id. the second request (cancel button) can pass the request id and call cancel on the token (if found).

this will be more complex if using a webfarm unless you use sticky sessions.

If your application is hosted by IIS with in-process hosting, a user will be able to cancel the process at the server side according to request from the user. The request means clicking X button on the browser, depressing Esc key on keyboard or executing XMLHttpRequest.abort() method for ajax request.

Below is sample:

Controller / Action Method

using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using MvcCore5App4.Models;
using System.Diagnostics;
using Microsoft.AspNetCore.Authorization;
using System.Threading;
using System.Threading.Tasks;
using System;
using Microsoft.AspNetCore.Identity;
using MvcCore5App4.Data;
 
namespace MvcCore5App4.Controllers
{
    public class HomeController : Controller
    {
        private readonly ILogger<HomeController> _logger;
 
        public HomeController(ILogger<HomeController> logger)
        {
            _logger = logger;
        }
 
        public async Task<IActionResult> Cancel(CancellationToken token)
        {
            _logger.LogInformation($"start: {DateTime.Now:ss.fff}");
            await Task.Delay(5000, token);
            _logger.LogInformation($"end: {DateTime.Now:ss.fff}");
            return View();
        }
    }
}

View

@{
    ViewData["Title"] = "Cancel";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h1>Cancel</h1>

<input type="button" id="ajaxRequest" value="Ajax Request" />
<br />
<input type="button" id="abortButton" value="Abort" />
<br />
<div id="result"></div>

@section Scripts {
    <script type="text/javascript">
        //<![CDATA[

        var xhr;

        $(function () {
            $('#ajaxRequest').on('click', function (e) {
                xhr = $.ajax({
                    url: '/home/cancel',
                    method: 'get',
                }).done(function (response) {
                    $("#result").empty;
                    $("#result").text(response);
                }).fail(function (jqXHR, textStatus, errorThrown) {
                    $("#result").empty;
                    $("#result").text('textStatus: ' + textStatus +
                        ', errorThrown: ' + errorThrown);
                });
            });

            $('#abortButton').on('click', function (e) {
                if (xhr) {
                    xhr.abort();
                }
            });
        });
        //]]>
    </script>

}

For detail please read the following article:

Handling aborted requests in ASP.NET Core