Invalid Expression Term 'Else'

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            Form a = new Form2();
            string Username = "Username";
            string Password = "Password";
            if ((textBox1.Text == Username) & (textBox2.Text == Password)) ;
            a.ShowDialog(); 
           
            else
            {
            
                a.Close();
            }
        }
    }
}