Active Directory login

public static bool User() 
{
    bool validation;
    try
    {
        LdapConnection lcon = new LdapConnection(new LdapDirectoryIdentifier((string)null, false, false));
        NetworkCredential nc = new NetworkCredential(Environment.UserName, "kals123", Environment.UserDomainName);
        lcon.Credential = nc;
        lcon.AuthType = AuthType.Negotiate;
        lcon.Bind(nc); // user has authenticated at this point, as the credentials were used to login to the dc.
        validation = true;
    }
    catch (LdapException)
    {
        validation = false;
    }
    return validation;
}

public static void getUser()
{
    DirectoryEntry directoryEntry = new DirectoryEntry("WinNT://" + Environment.UserDomainName);
    string userNames = "";
    string authenticationType="";
    foreach (DirectoryEntry child in directoryEntry.Children)
    {
        if (child.SchemaClassName == "User")
        {
            userNames += child.Name + Environment.NewLine; //Iterates and binds all user using a newline
            authenticationType += child.Username + Environment.NewLine;
        }
    }
    Console.WriteLine("************************Users************************");
    Console.WriteLine(userNames);
    Console.WriteLine("*****************Authentication Type*****************");
    //Console.WriteLine(authenticationType);
}

public static void fnGetListOfUsers() {
    // set up domain context
    PrincipalContext ctx = new PrincipalContext(ContextType.Domain);

    // find the group in question
    GroupPrincipal group = GroupPrincipal.FindByIdentity(ctx, "USERS");

    // if found....
    if (group != null)
    {
        // iterate over members
        foreach (Principal p in group.GetMembers())
        {
            Console.WriteLine("{0}: {1}", p.StructuralObjectClass, p.DisplayName);
            // do whatever you need to do to those members
        }
    }
}

public static void fnImp() {
    using (var context = new PrincipalContext(ContextType.Domain, Environment.UserDomainName))
    {
        using (var searcher = new PrincipalSearcher(new UserPrincipal(context)))
        {
            foreach (var result in searcher.FindAll())
            {
                DirectoryEntry de = result.GetUnderlyingObject() as DirectoryEntry;
                if ((string)de.Properties["givenName"].Value == Environment.UserName)
                {
                    //Console.WriteLine("First Name: " + de.Properties["givenName"].Value);
                    //Console.WriteLine("Last Name : " + de.Properties["sn"].Value);
                    //Console.WriteLine("SAM account name   : " + de.Properties["samAccountName"].Value);
                    //Console.WriteLine("User principal name: " + de.Properties["userPrincipalName"].Value);
                    Console.WriteLine();
                    PropertyCollection pc = de.Properties;
                    foreach (PropertyValueCollection col in pc)
                    {
                        Console.WriteLine(col.PropertyName + " : " + col.Value);
                        Console.WriteLine();
                    }
                }
            }
        }
    }
    Console.ReadLine();
}