How to get dynamically created checkboxes' value

I have a Users table in my Webforms ASP.NET 4.5 application which is filled dynamically with users. In that table there are checkboxes before the each username. I want to delete all the users which i checked after i click a delete button. However, when i click delete button, although button clicked event is called, checkedchanged event of checked checkboxes is not called. How can i get these checked checkboxes' value when i click the delete button?

using Microsoft.AspNet.Identity;
using Microsoft.AspNet.Identity.EntityFramework;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace WebApplication3.Account
{
    public partial class Register : System.Web.UI.Page
    {
        private UserStore<IdentityUser> userStore;
        private UserManager<IdentityUser> userManager;
        private List<string> users = new List<string>();
        protected void Page_Load(object sender, EventArgs e)
        {
            userStore = new UserStore<IdentityUser>();
            userManager = new UserManager<IdentityUser>(userStore);
            if (!IsPostBack)
            {
                fillTable();
            } 
        }

        private void fillTable()
        {
            TableHeaderRow headerRow = new TableHeaderRow();
            TableHeaderCell hCell1 = new TableHeaderCell();
            hCell1.CssClass = "col-md-1";
            hCell1.Text = "#";
            TableHeaderCell hCell2 = new TableHeaderCell();
            hCell2.Text = "Kullanıcı Adı";
            hCell2.CssClass = "col-md-5";
            headerRow.Controls.Add(hCell1);
            headerRow.Controls.Add(hCell2);
            headerRow.Controls.Add(new TableHeaderCell() { CssClass = "col-md-3" });
            headerRow.Controls.Add(new TableHeaderCell() { CssClass = "col-md-3" });
            headerRow.TableSection = TableRowSection.TableHeader;
            tblUser.Rows.Add(headerRow);

            foreach (IdentityUser user in userManager.Users.ToList())
            {
                TableRow row = new TableRow();
                TableCell cell1 = new TableCell();
                CheckBox checkBox = new CheckBox();
                checkBox.InputAttributes.Add("value", user.Id);
                checkBox.CheckedChanged += checkBox_CheckedChanged;
                cell1.Controls.Add(checkBox);
                cell1.HorizontalAlign = HorizontalAlign.Center;
                TableCell cell2 = new TableCell();
                cell2.Text = user.UserName;
                TableCell cell3 = new TableCell();
                HyperLink link = new HyperLink();
                link.Text = "Şifreyi Değiştir";
                cell3.Controls.Add(link);
                row.Controls.Add(cell1);
                row.Controls.Add(cell2);
                row.Controls.Add(new TableCell());
                row.Controls.Add(cell3);
                tblUser.Rows.Add(row);
                row.TableSection = TableRowSection.TableBody;
            }
        }

        void checkBox_CheckedChanged(object sender, EventArgs e)
        {
            if (ViewState["userList"] != null)
            {
                users = (List<string>)ViewState["userList"];
            }
            CheckBox checkbox = (CheckBox)sender;
            if (checkbox.Checked)
            {
                if (!users.Contains(checkbox.InputAttributes["value"]))
                {
                    users.Add(checkbox.InputAttributes["value"]);
                }
            }
            else
            {
                if (users.Contains(checkbox.InputAttributes["value"]))
                {
                    users.Remove(checkbox.InputAttributes["value"]);
                }
            }

            ViewState["userList"] = users;
        }

        protected void btnDeleteUser_Click(object sender, EventArgs e)
        {
            foreach (string id in users)
            {
                IdentityUser user = userManager.FindById(id);
                userManager.Delete(user);
            }
            fillTable();
        }

    }
}