Login.aspx.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Xml;
using System.Xml.Linq;
using System.Xml.XPath;

namespace workingtruefalsequiz1.Account
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                Label1.Text = "";
                Label2.Text = "";
                Label3.Text = "";
                Label4.Text = "";

            }
        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            string enteredUsername = TextBox1.Text;
            string enteredPassword = Password1.Value;

            if (!File.Exists("C:\\temp\\students.xml"))
            {
                Label1.Text = "No registered users";
            }
            else
            {
                var doc = XDocument.Load("C:\\temp\\students.xml");
                //int descendantsCount = doc.Descendants().Count(); // counts ALL descendants elements
                int childrenCount = doc.Root.Elements().Count(); //number of students
                bool userLoggedIn = false;

                for (int i = 0; i < childrenCount && !userLoggedIn; i++)
                {
                    XElement student = doc.Root.Elements("student").ElementAt(i);

                    if (student.Element("username").Value.Equals(enteredUsername))
                    {

                        if (student.Element("password").Value.Equals(enteredPassword))
                        {
                            Label1.Text = "Logged in";
                            userLoggedIn = true;
                            Session["boolLoggedIn"] = userLoggedIn;
                            Session["username"] = enteredUsername;
                            Session["id"] = i;
                            Response.Redirect("~/quiz.aspx");
                        }
                    }
                }
                if (!userLoggedIn)
                {
                    Label1.Text = "Not logged in";
                    this.Controls.Add(new LiteralControl("<a href='~/Accounts/Register.aspx'>Register now?</a>"));
                }
            }
        }
    }
}