HttpGet和HttpPost返回验证错误并加载SelectList

Question

I have a form which is based on a ViewModel that prompts the user to change a Person's XApplication status to either Accepted or Rejected.

When I submit the form via POST I want to Create a new XApplication and then if successful take the user back to the same page. If it contains errors then I wish to reload the form again, by passing View(personApp) , which will display the errors via the razor method @Html.ValidationSummary() .

However when I try and do this the View() doesn't know about my SelectLists and can't populate the dropdown with "Application Accepted" and "Application Rejected".

Is there another approach I can take?

[Route("student/xApplication/{personId?}")]
[HttpGet]
public ActionResult xApplication(int? personId)
{
    if (personId == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }
    Person person = db.People.Find(personId);
    if (person == null)
    {
        return HttpNotFound();
    }

    // Prepare ViewModel to pass to view, based on personId
    PersonViewModel personVModel = new PersonViewModel();
    personVModel.Person = person;

    // Get XApplication Data
    var xApps = from a in db.XApplications where a.personId == personId select a;

    XApplication personXApplication = null;
    if (xApps.Count() > 0)
    {
        personXApplication = xApps.First();
    }
    personVModel.XApplications = personXApplication;

    List<SelectListItem> applicationStatusItems = new List<SelectListItem>();
    applicationStatusItems.Add(new SelectListItem { Value = "1", Text = "Application Accepted" });
    applicationStatusItems.Add(new SelectListItem { Value = "0", Text = "Application Rejected" });
    SelectList applicationStatusList = new SelectList(applicationStatusItems, "Value", "Text", null);

    personVModel.ApplicationStatusList = applicationStatusList;

    return View(personVModel);
}

[HttpPost]
[Route("student/xApplication")]
public ActionResult xApplication(PersonViewModel personVModel)
{
    if (ModelState.IsValid)// Checks no errors
    {
        db.XApplications.Add(personVModel.XApplications);
        db.SaveChanges();
        return Redirect("/student/xApplication/" + personVModel.Person.id);
    }

    return View(personVModel);
}

Answer 1

Since the SelectList is hard coded, I would suggest generating them inside PersonViewModel to avoid code duplication. You can do so by moving the code that generates the SelectList to a public method named PopulateApplicationStatusList and call it in the constructor

public class PersonViewModel
{
    public PersonViewModel()
    {
        this.PopulateApplicationStatusList();
    }

    public SelectList ApplicationStatusList { get; set; }

    public void PopulateApplicationStatusList()
    {
        List<SelectListItem> applicationStatusItems = new List<SelectListItem>();
        applicationStatusItems.Add(new SelectListItem { Value = "1", Text = "Application Accepted" });
        applicationStatusItems.Add(new SelectListItem { Value = "0", Text = "Application Rejected" });
        this.ApplicationStatusList = new SelectList(applicationStatusItems, "Value", "Text", null);
    }
}

In your get action method, ApplicationStatusList will be generated when you create a new instance of PersonViewModel

[Route("student/xApplication/{personId?}")]
[HttpGet]
public ActionResult xApplication(int? personId)
{
    if (personId == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }
    Person person = db.People.Find(personId);
    if (person == null)
    {
        return HttpNotFound();
    }

    // Prepare ViewModel to pass to view, based on personId
    PersonViewModel personVModel = new PersonViewModel(); // ApplicationStatusList is generated here
    personVModel.Person = person;

    // Get XApplication Data
    var xApps = from a in db.XApplications where a.personId == personId select a;

    XApplication personXApplication = null;
    if (xApps.Count() > 0)
    {
        personXApplication = xApps.First();
    }
    personVModel.XApplications = personXApplication;

    return View(personVModel);
}

In your post action method, you can repopulate ApplicationStatusList property when there's any errors by calling PopulateApplicationStatusList method

[HttpPost]
[Route("student/xApplication")]
public ActionResult xApplication(PersonViewModel personVModel)
{
    if (ModelState.IsValid)// Checks no errors
    {
        db.XApplications.Add(personVModel.XApplications);
        db.SaveChanges();
        return Redirect("/student/xApplication/" + personVModel.Person.id);
    }

    // repopulate ApplicationStatusList property
    personVModel.PopulateApplicationStatusList();

    return View(personVModel);
}