MVC数据在视图中传递

Question

I am making my MVC application. I open my view with predefined parameters like this:

return RedirectToAction("PickGroupForHomework", "Account", new {subject_id = id, qty=model.qty });

And this works fine, the data subject_id and qty are passed correctly. However, my view PickGroupForHomework contains a form to fill, which is then validated. If the input is not valid, the window simply should reload with the data subject_id and qty as defined in previous view. I do this in such way:

public ActionResult PickGroupForHomework(PickGroupForHomeworkViewModel model)
        {
            ClassDeclarationsDBEntities2 entities = new ClassDeclarationsDBEntities2();
            model.groups = entities.Groups.ToList();
            model.users = entities.Users.ToList();
            int id = model.subject_id;
            var subj = entities.Subjects
                    .Where(b => b.class_id == model.subject_id)
                    .FirstOrDefault();
            if (subj != null)
            {
                model.subject_name = subj.name;
            }
            if (ModelState.IsValid)
            {

            }
            else
            {
                return View(model);
            }
            return View(model);

        }

But the resulting URL does not contain the data I need, but just a plain view. How do I do it right?

Answer 1

In order for you wep app to work, you will need two actions, one to set your model up for the View and another to actually do the work to post and save your data:

    public ActionResult PickGroupForHomework(int subject_id, int qty)
    {
        //Initialize your model here. Below is just an example.
        ClassDeclarationsDBEntities2 entities = new ClassDeclarationsDBEntities2();

        PickGroupForHomeworkViewModel model = new PickGroupForHomeworkViewModel();

        model.groups = entities.Groups.ToList();
        model.users = entities.Users.ToList();

        model.subject_id = subject_id;
        model.qty = qty;

        return View("PickGroupForHomework", model);
    }

    [HttpPost]
    public ActionResult PickGroupForHomework(PickGroupForHomeworkViewModel model)
    {
        ClassDeclarationsDBEntities2 entities = new ClassDeclarationsDBEntities2();

        int id = model.subject_id;

        var subj = entities.Subjects
                .Where(b => b.class_id == model.subject_id)
                .FirstOrDefault();

        if (subj != null)
        {
            model.subject_name = subj.name;
        }
        if (ModelState.IsValid)
        {
            //Save to database
            [code goes here]

            //return to a View to show your results
            return View("[Your view to see the results]")
        }

        //Model Validation did not pass
        //or exception occurred go back to View
        return View(model);
    }