Eto na ung connection string natin

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;
using System.Data.SqlClient;
using System.Data.Sql;

namespace Database
{
    public partial class Form1 : Form
    {
        private SqlConnection connection = new SqlConnection();
        byte counter = 4;
        byte count = 0;
        string user = null;
        string cString = "Data Source=.\\SQLEXPRESS;AttachDbFilename=\"c:\\users\\user\\documents\\visual studio 2010\\Projects\\Database\\Database\\nbiCCMdb.mdf\";Integrated Security=True;Connect Timeout=30;User Instance=True";
        public Form1()
        {
            InitializeComponent();
            connection.ConnectionString = cString;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            connection.Close();
            Application.Exit();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                connection.Open();
                SqlCommand command = new SqlCommand();
                command.Connection = connection;
                command.CommandText = "SELECT * FROM userTable WHERE userName = '" + textBox1.Text + "' AND userPass = '" + textBox2.Text + "'";
                SqlDataReader reader = command.ExecuteReader();
                textBox1.Select();
                while (reader.Read())
                {
                    count++;
                }
                if (count == 1)
                {
                    user = textBox1.Text;
                    textBox1.Clear();
                    textBox2.Clear();
                    connection.Close();
                    this.Hide();
                }
                else if (count != 1 && !(textBox1.Text == String.Empty || textBox2.Text == String.Empty))
                {
                    counter--;
                    if (counter != 0)
                    {
                        MessageBox.Show("Incorrect Username/Password please try again." + Environment.NewLine +
                        "You have " + counter + " tries left.");
                        textBox2.Clear();
                        textBox2.Focus();
                    }
                }
                else
                {
                    MessageBox.Show("Please enter Username/Password.");
                    if (textBox1.Text == String.Empty)
                    {
                        textBox1.Focus();
                    }
                    else
                    {
                        textBox2.Focus();
                    }
                }
                if (counter == 0)
                {
                    MessageBox.Show("You Have Exceeded The Acceptable Amount Of Trials" + Environment.NewLine +
                    "Program Terminated.");
                    connection.Close();
                    Application.Exit();
                }
                connection.Close();
            }
            catch(Exception ex)
            {
                MessageBox.Show("Error " + ex);
                connection.Close();
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            textBox1.Select();
        }
    }
}