Нет подключения к БД

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace WindowsFormsApplication3
{
    public partial class Form1 : Form
    {
        //Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\DataBase.mdf;Integrated Security=True;Connect Timeout=30
 
        /*  string Login = textBox1.Text;
          string Password = textBox2.Text;*/
        public int id;
        public Form1()
        {
            InitializeComponent();
        }
 
        private void Form1_Load(object sender, EventArgs e)
        {
 
 
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            Avtorization();
        }
 
        //  string Avtorization(string login, string password)
        string Avtorization()
        {
 
            //////////////////////////////////////////////////////////////////
            string connectString =
                 "Server=(local);" +
                 "Integrated Security=true";
            SqlConnectionStringBuilder builder =
                new SqlConnectionStringBuilder(connectString);
            builder.AttachDBFilename = @"D:\Projects\C++\VS 12 (3 Kourse)\WindowsFormsApplication2\WindowsFormsApplication2\bin\Debug\DataBase.mdf";
            SqlConnection connection = new SqlConnection(builder.ConnectionString);
            ////////////////////////////////////////////////////////////////
 
           // string ConnectionString = "Server=.\\SQLEXPRESS;Database=DataBase;Integrated Security=True";
           // string ConnectionString = "Database=DataBase;Server=(local);Integrated Security=True"; //DataBaseConnectionString
         //   string ConnectionString = "Data Source=(LocalDB)\v11.0;Integrated Security=True;Connect Timeout=30";
            //string ConnectionString = GetConnectionString();
            string SelectQuery = "SELECT Id FROM Actors WHERE Login = '" + textBox1.Text + "'";
            //using (SqlConnection Connection = new SqlConnection(ConnectionString));
           // SqlConnection Connection = new SqlConnection(ConnectionString);///////////////
       ///////////
            /*     SqlConnection connection = new SqlConnection(builder.ConnectionString);
            SqlCommand Command = new SqlCommand(SelectQuery, Connection);
            Connection.Open();
            SqlDataReader Reader = Command.ExecuteReader();
            string Speciality = null;
                while (Reader.Read())
                {
                    string str = Reader.GetValue(0).ToString();
                   if (textBox1.Text == str)
                    {
                        MessageBox.Show(str);
                        break;
                    }
                    
                }
                Reader.Close();
                Connection.Close();
            return Speciality;
        }*/   ////////////////////////
        connection.Open();
            MessageBox.Show("Connected");
            connection.Close();
            return null;
       /* static private string GetConnectionString()
        {
            
            return "Data Source=MSSQL1;Initial Catalog=DataBase"
                + "Integrated Security=true;";
        }*/
 
    }
    }
}

connection.Open();

try
{
    connection.Open();
}
catch(Exception E)
{
    MessageBox.Show(E.Message);
}