Adding new data to multiple tables using dropdownlist

Question

Using MVC4 am wanting to implement functionality which will allow a user to add new items to the database.

I've managed to achieve this adding items to a single table, but now I need to display data from multiple tables, then populate the added / selected data to those tables.

I have these 3 tables

Threats

ID
Description

ThreatHasSecurityEvent

ThreatID
SecurityEventID

SecrutiyEvents

ID
Description

And here's my code so far:

ViewModel

  public class ThreatWithSecurityEvents
    {
        public Threat Threat { get; set; }
        public SecurityEvent SecurityEvent { get; set; }
        public List<int> SecurityEventIds { get; set; }

        public ThreatWithSecurityEvents()
        {
            SecurityEventIds = new List<int>();
        }
    }

Get Controller

  [HttpGet]
        public ActionResult AddNewThreat()
        {
            ThreatWithSecurityEvents ViewModel = new ThreatWithSecurityEvents();
            var SecurityEvents = _DBContext.SecurityEvents.Select(x => new SelectListItem()
            {
                Text = x.Description,
                Value = x.ID.ToString()
            });
            ViewBag.SecurityEventDropdown = SecurityEvents;

            return View(ViewModel);
        }

View

@model  RiskAssesmentApplication.Models.ThreatWithSecurityEvents

@{
    ViewBag.Title = "AddNewThreat";
    //Layout = "~/Views/Shared/MasterLayout.cshtml";
}

<div style="font-family: Calibri">
<h2>AddNewThreat</h2>

@using (Html.BeginForm()) {
    @Html.AntiForgeryToken()
    @Html.ValidationSummary(true)

    <fieldset>
        <legend>Threat</legend>
        @using (Html.BeginForm("Add New Threat", "Threats"))
        {
        Html.HiddenFor(model => model.SecurityEventIds);
        <div class="editor-label">
            @Html.LabelFor(model => @Model.Threat.Description, "Threat Description")
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => @Model.Threat.Description)
            @Html.ValidationMessageFor(model => @Model.Threat.Description)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => @Model.SecurityEvent.Description, "Associated Security Event")
        </div>
        <div class="editor-field">
            @Html.DropDownListFor(x => x.SecurityEventIds, ViewBag.SecurityEventDropdown as IEnumerable<SelectListItem>)
        </div>
        <p>
            <input type="submit" value="Add New" />
        </p>
        }
    </fieldset>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

    </div>

Am unsure how to implement the Post Action Method and a Save Method in the repository. Previously I could inject a new Threat Object and send it to the edit view doing something like:

Previous Get Method - AddNewThreat

[HttpGet]
    public ActionResult AddNewThreat()
    {
        return View("EditThreat", new Threat());
    }

and I would then use the EditThreat Action Method to post back

Previous Post Action - AddNewThreat

[HttpPost]
        public ActionResult EditThreat(Threat Threat)
        {
            if (ModelState.IsValid)
            {
                repository.SaveThreat(Threat);
                TempData["message"] = string.Format("{0} new description has been saved", Threat.Description);
                return RedirectToAction("GetThreat", new { ThreatID = Threat.ID });
            }
            else
            {
                // something is incorrect!
                return View(Threat);
            }
        }

Previous Save Method - SaveThreat From Repository

 public void SaveThreat(Threat Threat)
        {
            if (Threat.ID == 0)
            {
                _context.Threats.Add(Threat);
            }
            else
            {
                Threat dbEntry = _context.Threats.Find(Threat.ID);
                if (dbEntry != null)
                {
                    dbEntry.Description = Threat.Description;
                }
            }
        _context.SaveChanges();
    }

That's as far as I have got so far.

I want the user to be able to enter a new threat description and then select a security event or multiple events from a drop down list which will be associated with the new threat.

I realize am going to have to change the post back action method in the controller and the Save method in my repository, but I cant work out how to get both the new Threat description and the existing security events saved back to the database. I've had a search but as of yet haven't found / understood anything.

Any advice/help would be great.

Thanks

First your need to remove Html.HiddenFor(model => model.SecurityEventIds); (you cant generate a hidden input for a complex objects or collection). Next use @Html.ListBoxFor(x => x.SecurityEventIds, ViewBag.....) so it generates a multiple select (i.e you can select one of more SecrutiyEvents). Then post back the model, save the new Threat and based on its new ID, save each selected SecrutiyEvent to the ThreatHasSecurityEvent table — user3559349
– user3559349, Commented Jul 24, 2015 at 12:14
Also your view model does not need public SecurityEvent SecurityEvent { get; set; }, but it should contain int ThreatID and string Description instead of Threat Threat and it should also include public SelectList SecurityEventList { get; set; } so you don't need to use ViewBag — user3559349
– user3559349, Commented Jul 24, 2015 at 12:18
Thanks Stephen, I haven't quite got it working yet but am getting there. I'll be sure to update. — Erick Bongo
– Erick Bongo, Commented Jul 25, 2015 at 11:15

user3559349 · Accepted Answer · 2015-07-26 00:29:43Z

You view model should be

public class NewThreatVM
{
  public string Description { get; set; } // add validation attributes as required
  public List<int> SelectedSecurityEvents { get; set; }
  public SelectList SecurityEventList { get; set; } // or IEnumerable<SelectListItem>
}

Side note: The Threat.ID property is not required in a create view, however if your want to use this for editing an existing Threat as well, add property int? ID and use if (model.ID.HasValue) in the POST method to determine if its a new or existing Threat

and the simplified view

@model yourAssembly.NewThreatVM
@Html.BeginForm())
{
  @Html.TextBoxFor(m => m.Description)
  @Html.ListBoxFor(m => m.SelectedSecurityEvents, Model.SecurityEventList)
  <input type="Submit" value="Create" />
}

Side notes: Your view should not include a hidden input for the Security Event ID's (you cannot bind an input to a complex object or collection)

then the controller

public ActionResult Create()
{
  NewThreatVM model = new NewThreatVM model();
  ConfigureViewModel(model);
  return View(model);
}

[HttpPost]
public ActionResult Create(NewThreatVM model)
{
  if (!ModelState.IsValid)
  {
    ConfigureViewModel(model);
    return View(model);
  }
  // Initialize new data model and map properties from view model
  Threat threat = new Threat() { Description = model.Description };
  // Save it (which will set its ID property)
  _context.Threats.Add(Threat);
  _context.SaveChanges();
  // Save each selected security event
  foreach (int selectedEvent in model.SelectedSecurityEvents)
  {
    ThreatHasSecurityEvent securityEvent = new ThreatHasSecurityEvent()
    {
      ThreatID = threat.ID,
      SecurityEventID = selectedEvent
    };
    _context.ThreatHasSecurityEvents.Add(securityEvent);
  }
  _context.SaveChanges();
  return RedirectToAction("GetThreat", new { ThreatID = threat.ID });
}

private void ConfigureViewModel(NewThreatVM model)
{
  var securityEvents = _context.SecurityEvents;
  model.SecurityEventList = new SelectList(securityEvents, "ID", "Description");
}

Thanks for the example and explanation, this has really helped, I was really stumped on how to pass back the view model and map it's properties to a new threat and then do the same with the security event. I was actual trying to map back to an instance of Security Event, I created a mess.. (face palm!!).

Fabio · Accepted Answer · 2015-07-24 11:55:55Z

1

I believe the easiest way to achieve this, is "dividing" your form into separated steps.

You have2 entities: Threats, SecurityEventID

Threat has a collection of SecurityEvents

Create a form to add/edit Threats (url: Threats/Add | Threats/Edit/ThreatId)
Create a form to add/delete Events of an existing Threat (url: Threats/AddEvent/ThreatIdHere

Use custom ViewModels instead of the original class to send data to controller. Examples:

public class AddThreatViewModel
{
   public string Description { get; set; }
   //since it's a add view model, we dont need a ThreatId here
}

[HttpPost]
public ActionResult AddThreat(AddThreatViewModel model)
{
    //convert the view model to Threat, add to database
}


public class AddThreatEvent
{
    public int ThreatId { get; set; }
    public int SecrutiyEventId { get; set; }
}

[HttpPost]
public ActionResult AddThreatEvent(AddThreatEventmodel)
{
    //add threat event into existing threat
}

answered Jul 24, 2015 at 11:55

Fabio

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1 Comment

Erick Bongo Over a year ago

Thanks Fabio, haven't quite got it working but will update when I have.

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