How can i pass complex object from view to controller with POST - ASP.NET MVC

Question

Hi i tried to find a fix to my problem but i cant. I have a class with one Thesis and many keywords

public class ThesisWithKeywordsModel
    {
        public Thesis thesis { get; set; }
        public IQueryable<Keyword> keywords { get; set; }
        public IEnumerable<int> checkboxList { get; set; }
    }

Action

        [HttpGet]
        public ActionResult CreateThesis()
        {
            ThesisWithKeywordsModel thesis = new ThesisWithKeywordsModel();
            thesis.thesis = new Thesis();
            thesis.keywords = db.KeywordRepository.GetAllKeywords();
            thesis.checkboxList = new List<int>();
            return View(thesis);
        }

where I use thesis.keywords to show list of checkbox buttons and I put thesis.checkboxList to save returned result from view who must be ICollection(int) id's from checked checkbox buttons.

Here is my View

@model SearchSystem.Models.ThesisWithKeywordsModel

@{
    var listField = new List<SelectListItem>();
    listField.Add(new SelectListItem() { Text = "Софтуер", Value = "Софтуер", Selected = true });
    listField.Add(new SelectListItem() { Text = "Хардуер", Value = "Хардуер" });
    listField.Add(new SelectListItem() { Text = "Мрежи", Value = "Мрежи" });

    var listFree = new List<SelectListItem>();
    listFree.Add(new SelectListItem() { Text = "Свободна", Value = "Свободна", Selected = true });
    listFree.Add(new SelectListItem() { Text = "Заета", Value = "Заета" });
}

@using (Html.BeginForm("CreateThesis", "ProfessorProfile", FormMethod.Post))
{
     <table class="table">
        <tr>
            <td>@Html.LabelFor(x => x.thesis.ThesisTitle)</td>
            <td>@Html.EditorFor(x => x.thesis.ThesisTitle)</td>  
        </tr>
        <tr>
             <td>@Html.LabelFor(x => x.thesis.ThesisDescription)</td>
             <td>@Html.EditorFor(x => x.thesis.ThesisDescription)</td>
        </tr>
        <tr>
             <td>@Html.LabelFor(x => x.thesis.Field)</td>
             <td>@Html.DropDownList("Field", listField)</td>
        </tr>
         <!--<tr>
             <td>@Html.LabelFor(x => x.thesis.Free)</td>
             <td>@Html.DropDownList("Free", listFree)</td>
         </tr>-->
    </table>

    foreach(var keyword in Model.keywords)
    {
        <input type="checkbox" id="@keyword.KeywordId" name="checkboxList" value="@keyword.KeywordId">
        <label for="@keyword.KeywordId">@keyword.Value</label><br/>
    }

    <input type="submit" value="Create"/>
}

and here is my other action

[HttpPost]
        public ActionResult CreateThesis(ThesisWithKeywordsModel thesis)
        {
            if (ModelState.IsValid)
            {
                var loggedProfessorId = db.ProfessorRepository.GetProfessorIDByUserName(User.Identity.Name);
                if (loggedProfessorId != 0)
                {
                    var professor = db.ProfessorRepository.GetProfessorById(loggedProfessorId);
                    db.ProfessorRepository.AddThesis(professor, thesis.thesis);
                    return RedirectToAction("MyTheses");
                }
                return RedirectToAction("Login", "Account");
            }
            return View(thesis);
        }

The problem is the object ThesisWithKeywordsModel thesis is null, thesis.thesis, thesis.checkboxList are both null. Funny thing is that when i see response in response body I have POST parameters and if I change ThesisWithKeywordsModel thesis with Thesis thesis i have all values that i post from form.

Answer 1

Firstly I would not attempt to use IQueryable for your Keywords property, better would be to use IList. Secondly it would probably be better to combine Keywords and CheckboxList into a single property, having your keyword class something like this:

public class Keyword
{
    public int KeywordId {get;set;}
    public bool Checked {get;set;}
}

So ThesisWithKeywordsModel would look like this:

public class ThesisWithKeywordsModel
{
    public Thesis thesis { get; set; }
    public IList<Keyword> keywords { get; set; }
}

Then in your controller, you should be able to do:

thesis.keywords = db.KeywordRepository.GetAllKeywords()
                     .Select(kw => new Keyword
                     {
                        KeyeordId = kw.KeywordId,
                        Checked = false
                     }).ToList();

Next you need to change your foreach loop in the cshtml into a for loop when passing a list of values to/from the view.

for(var i = 0; i < Model.keywords.Count; i++)
{
    <input type="checkbox" id="@Model.keywords[i].KeywordId" name="checkboxList" checked='@Model.keywords[i].Checked ? "checked" : ""'>
    <label for="@Model.keywords[i].KeywordId">@Model.keywords[i].Value</label><br/>
}