public void InsertData()
{
    SqlConnection conn;
    SqlCommand cmd;
    string cmdString = @"Insert Customers (CustomerID, CompanyName, 
       ContactName) Values ('BILLE', 'XYZ Company', 'Bill Evjen')";
    conn = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\NORTHWND.MDF;Integrated Security=True;User Instance=True");
    cmd = new SqlCommand(cmdString, conn);
    conn.Open();

    cmd.ExecuteNonQuery();
    conn.Close();
}
