public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
  
        }

        public bool ValidateApplicationUser(string userName, string password)
        {
      
            {
        
                var AuthContext = new DataClasses1DataContext();
          
           
                var query = from c in  AuthContext.Users
                            where (c.Username == userName.ToLower() && c.Password == password.ToLower())
                            select c;

              
                if(query.Count() != 0 )
                {
                    return true;
                }

                return false;}

 }

        private void Login(object sender, RoutedEventArgs e)
        {

      bool authenticated = true;
 
            {
                if (usernameTextBox.Text !="" && passwordTextBox.Text != "")
                {
                    authenticated = ValidateApplicationUser(usernameTextBox.Text , passwordTextBox.Text);
                }
               
        
            if (!authenticated)
            {
                MessageBox.Show("Invalid login. Try again.");
            }
            else
            {
                MessageBox.Show("Congradulations! You're a valid user!");

              
               Window3 c = new Window3();
              c.ShowDialog();
                this.Close();
            }

        }
    }