connection string for sqlexpress ,stumpted

I am getting "keyword not supported" for my connection string. I have tried to edit it a lot but getting nowhere.
Please help me with the connection string

Code:

---

using System.Data.SqlClient;
namespace Gymdata4
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            SqlConnection thisConnection = new SqlConnection( "Data Source=.\\SQLEXPRESS;AttachDbFilename=""+"C:\\Documents and Settings\\Michael\\My Documents\\GymData3.mdf""+"Integrated Security=True;Connect Timeout=30;User Instance=True");
            SqlDataAdapter thisAdapter = new SqlDataAdapter("SELECT * FROM customers", thisConnection);
            SqlCommandBuilder thisBuilder = new SqlCommandBuilder(thisAdapter);
            DataSet thisDataSet = new DataSet();
            thisAdapter.Fill(thisDataSet, "customers");
        }

---

Firstly I'd suggest usiong a verbatim string literal so you don't have to double-up your slashes.

Secondly, if you want to access a database in the current user's My Documents folder then I suggest that you don't hard-code it:

C# Code:

SqlConnection thisConnection = new SqlConnection(string.Format(@"Data Source=.\SQLEXPRESS;AttachDbFilename={0}\GymData3.mdf;Integrated Security=TrueUser Instance=True",
                                                               Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)));

Useful site: www.connectionstrings.com