How to make it so that only authenticated users can access a page in an ASP .NET project

Question

I'm trying to make is so that after logging in to a site, the application automatically redirects the user to the default page of the application. Also, it is important that the user cannot access anything other than the login webpage without being logged in. I've been stuck on this for 3 days now. We have a horrible professor who doesn't do his documentation right (I have to google everything instead of having it in the scripts or something)

The user's credentials are hardcoded inside of the Web.config file as keyed values. They are not checked against a database, only against the hardcoded strings.

This is the code that I have:

The design of the login page (it's the Login element from the toolbox, not something manually constructed).

This is the code of that page: Login.aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Configuration;

namespace LV1___Kalkulator
{
    public partial class Login : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected bool ValidateUser(String username, String password)
        {
            if (Login1.UserName == "tstipic" && // ConfigurationManager.AppSettings["korisnickoime"] &&
               Login1.Password == "password") //ConfigurationManager.AppSettings["sifra"])
            {
                return true;
            }
            else return false;
        }

        protected void Login1_Authenticate(object sender, AuthenticateEventArgs e)
        {
            if (e.Authenticated)
            {
                Response.Redirect("Dafault.aspx");
            }
            if (ValidateUser(Login1.UserName, Login1.Password))
            {
                Response.Redirect("Dafault.aspx");
            }
            else
            {
                e.Authenticated = false;
            }
        }
    }
}

This is my web.config file:

<?xml version="1.0" encoding="utf-8"?>

<!--
  For more information on how to configure your ASP.NET application, please visit
  https://go.microsoft.com/fwlink/?LinkId=169433
  -->
<configuration>    
  <system.web>

    <compilation debug="true" targetFramework="4.6.1"/>
    <httpRuntime targetFramework="4.6.1"/>
  </system.web>
  <system.codedom>
    <compilers>
      <compiler language="c#;cs;csharp" extension=".cs"
        type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
        warningLevel="4" compilerOptions="/langversion:default /nowarn:1659;1699;1701"/>
      <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb"
        type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
        warningLevel="4" compilerOptions="/langversion:default /nowarn:41008 /define:_MYTYPE=\&quot;Web\&quot; /optionInfer+"/>
    </compilers>
  </system.codedom>
  <appSettings>
    <add key="ValidationSettings:UnobtrusiveValidationMode" value="None" />
    <add key="korisnickoime" value="user"/>
    <add key="sifra" value="pass"/>
    </appSettings>
  <connectionStrings>
    <add name="konekcijaNaBazu"
       connectionString="Provider=Microsoft.Jet.OLEDB.4.0;
       Data Source=|DataDirectory|\ASP_Database.mdb"
       providerName="System.Data.OleDb"/>  
  </connectionStrings>
</configuration>

Edit: I have implemented what Albert D. Kallal advised. That seems to be a step in the right direction, but I'm still experiencing the same results. I input the correct credentials only to be presented with the login page anew.

Answer 1

Assuming you enabled security, then you need this in your config file:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <system.web>
       <authorization>
        <deny users="?"/>
       </authorization>
    </system.web>
</configuration>

What the above means and says: Do NOT allow anyone to hit a web page unless they are authenticated. If they are not authenticated, then the web server will automatic re-direct users to your logon page. The result is no web page can be hit unless they are logged on. If they manually type in a URL, then the web server will re-direct them to the logon page, because that's the page you setup as the logon page. That setting in web.config is

<authentication mode="Forms">
  <forms loginUrl="~/Account/Login.aspx" defaultUrl="~/Default.aspx" />
</authentication>

So above sets the default web page, but ALSO sets the page that everyone is re-directed to if they attempt to hit a web page without having been authenticated.