Ilya Galdin Ilya Galdin - 1 month ago 13
C# Question

MVC: POST controller method get empty Dictionary

My GET method of controller construct and fill Model, which including

Dictionary<int, MyClass>
, and transmit that to View. But after, POST controller method get not null model with empty Dictionary.

Model:

public class CheckBoxItem
{
public string Name { get; set; }
public double Data { get; set; }
public bool Selected { get; set; }
}
public class CreateNewEventModel
{
[Required(ErrorMessage = "Error text")]
[Display(Name = "Header name")]
public string EventName { get; set; }
public Dictionary<int, CheckBoxItem> CheckBoxDataItems { get; set; }
public CreateNewEventModel()
{
CheckBoxDataItems = new Dictionary<int, CheckBoxItem>();
}
}


Controller:

public ActionResult CreateEvent()
{
CreateNewEventModel model = new CreateNewEventModel();
// FILL MODEL
foreach (var user in db.UsersInfo.ToList())
{
model.CheckBoxDataItems.Add(user.Id, new CheckBoxItem()
{
Name = user.Name,
Data = 0,
Selected = false
});
}
// THERE IS FULL MODEL
return View(model);
}
[HttpPost]
public ActionResult CreateEvent(CreateNewEventModel model)
{
// THERE IS model.Event name include text
// BUT model.CheckBoxDataItems is empty
if (ModelState.IsValid)
{
...
return View(model);
}
return View(model);
}


View:

@model HLyaa.Models.CreateNewEventModel

@{
ViewBag.Title = "Create Event";
Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Создание события</h2>

@if (Model.CheckBoxDataItems.Count() != 0)
{
using (Html.BeginForm("CreateEvent", "Events", FormMethod.Post))
{
@Html.ValidationSummary()
<div>
@Html.LabelFor(model => model.EventName)
<div>
@Html.EditorFor(model => model.EventName)
</div>
</div>
<table>
@foreach (var kvpair in Model.CheckBoxDataItems)
{
<tr>
<td>
@Html.CheckBoxFor(model => model.CheckBoxDataItems[kvpair.Key].Selected)
</td>
<td>
@Html.DisplayFor(model => model.CheckBoxDataItems[kvpair.Key].Name)
@Html.HiddenFor(model => model.CheckBoxDataItems[kvpair.Key].Selected)
@Html.HiddenFor(model => model.CheckBoxDataItems[kvpair.Key].Name)
</td>
<td>
@Html.TextBoxFor(model => model.CheckBoxDataItems[kvpair.Key].Data, new { @type = "number" })
</td>
</tr>
}
</table>
<br />
<input type="submit" value="Next" />
}
}


How I can transmit data inside dictionary from View to Controller?

Answer

Dictionary no, List/Array yes, but you will have to make some modifications.

Modify models

public class CheckBoxItem {
    public int UserId { get; set; }
    public string Name { get; set; }
    public double Data { get; set; }
    public bool Selected { get; set; }
}

public class CreateNewEventModel {
    [Required(ErrorMessage = "Error text")]
    [Display(Name = "Header name")]
    public string EventName { get; set; }
    public List<CheckBoxItem> CheckBoxDataItems { get; set; }
    public CreateNewEventModel() {
        CheckBoxDataItems = new List<CheckBoxItem>();
    }
}

Modify GET method CreateEvent

public ActionResult CreateEvent() {
    var model = new CreateNewEventModel();
    //...FILL MODEL
    foreach (var user in db.UsersInfo.ToList()) {
        model.CheckBoxDataItems.Add(new CheckBoxItem() {
            UserId = user.Id,
            Name = user.Name,
            Data = 0,
            Selected = false
        });
    }
    // THERE IS FULL MODEL
    return View(model);
}

Update View

<table>
  @for (var i = 0; i < Model.CheckBoxDataItems.Count; i++) {
    <tr>
      <td>
        @Html.CheckBoxFor(model => model.CheckBoxDataItems[i].Selected)
      </td>
      <td>
        @Html.DisplayFor(model => model.CheckBoxDataItems[i].Name)
        @Html.HiddenFor(model => model.CheckBoxDataItems[i].UserId)
        @Html.HiddenFor(model => model.CheckBoxDataItems[i].Selected)
        @Html.HiddenFor(model => model.CheckBoxDataItems[i].Name)
      </td>
      <td>
        @Html.TextBoxFor(model => model.CheckBoxDataItems[i].Data, new { @type = "number" })
      </td>
    </tr>
  }
</table>

CheckBoxDataItems should be populated now when you post it to controller