C# Windows Authentication – Using Windows Authentication in ASP.NET with C#

Im trying to understand how windows authentication works and how to implement it. Ive read quite a few articles and watched some quite length videos on youtube but i still cant my head around what needs to be added to my web.config file/ index.aspx page to make it work properly.

Here is the index.aspx page:

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;
using System.Data;

namespace asset_management_system
{
  public partial class index1 : System.Web.UI.Page
  {

    DataAccessLayer dal = new DataAccessLayer();

    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void loginBut_Click(object sender, EventArgs e)
    {

        string username = usernameTB.Text.Trim();
        string password = passwordTB.Text.Trim();

        try
        {
            using (SqlDataReader dr = dal.CheckLoginDetails(username))
            {
                //if username does not exist
                if (!dr.Read())
                {
                    MessageBox.Show("Invalid login details");
                }

                else
                {
                    //if password matches the username then redirect to home page
                    if (dr[0].ToString() == password)
                    {
                        Session["username"] = username;
                        Response.Redirect("Home/home.aspx");
                    }
                    else
                    {
                        MessageBox.Show("Invalid login details");
                    }
                }
            }
        }
        catch (SqlException sqlex) { MessageBox.Show("There may be an issue with the server, please contact the administrator" +
                                                     " and provide this error message: " + sqlex); }
        catch (Exception ex) { MessageBox.Show("error message: " + ex); }


    }//end of loginBut_click method


  }//end of class
}//end of namespace

And here is the web.config file

<?xml version="1.0"?>

<configuration>

  <connectionStrings>
    <add name="Asset management System DBConnectionString" connectionString="Data Source=STEPHENP\SQLEXPRESS;Initial Catalog=&quot;Asset management System DB&quot;;Integrated Security=True" providerName="System.Data.SqlClient"/>
  </connectionStrings>

  <system.web>

    <compilation debug="true" targetFramework="4.0">
      <assemblies>
        <add assembly="System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
        <add assembly="System.Web.Extensions.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
        <add assembly="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
      </assemblies>
    </compilation>

    <authentication mode="Windows">
    </authentication>
    <identity impersonate="true"/>

  </system.web>

</configuration>