user registration form without entity framework using MVC :   [HttpPost]
        public ActionResult Create(UserModel userModel)
        {

            using (SqlConnection sqlCon= new SqlConnection(connectionString))
            {
                sqlCon.Open();
                String query = "INSERT INTO User VALUES(@UserName,@UserPassword,@UserAddress)";
                SqlCommand sqlCmd = new SqlCommand(query,sqlCon);
                sqlCmd.Parameters.AddWithValue("@UserName",userModel.username);
                sqlCmd.Parameters.AddWithValue("@UserPassword", userModel.userpassword);
                sqlCmd.Parameters.AddWithValue("@UserAddress", userModel.useraddress);

                sqlCmd.ExecuteNonQuery();


            }

            return RedirectToAction("Index");
        }



I'm learning C#.So I tried to code CURD operations.In this code there is is a Open() method..I want to know Why it used and explain line bye line what is code  flow..