@Html.Editor Model binding Issue

Question

I am trying to generate Two sets of List of checkboxes on a view. It all working apart from Post action. On submit, ParentViewModel is not binding the ChildViewModel properly Model. FirstCheckboxList Model. SecondCheckboxList Above both are coming as null.

I am not sure what I am missing. Any help on this would be great. Thanks in advance.

CheckboxItems.cshtml

@model List<CheckboxItem>
@{        
    for (int i = 0; i < Model.Count(); i++)
    {
       <div>
       @Html.CheckBoxFor(x => x.ElementAt(i).Checked, new { @id = Model.ElementAt(i).Id, onclick = "GetValue()" })
          <span id="Padded">@Model.ElementAt(i).Text</span>
       </div> 
    }
}

MainView.cshtml

 @Html.BeginForm(){     
       @Html.EditorFor(m=> m.FirstCheckboxList,"CheckboxItems") 
       @Html.EditorFor(m=> m.SecondCheckboxList, "CheckboxItems")                
 }
 @Html.TextBoxFor(m => m.FSelected, new Dictionary<string,object>() {{"readonly",true}})       
 @Html.TextBoxFor(m => m.FUniverse,new Dictionary<string,object>() {{"readonly",true}})
        <input type="submit" name="nextBtn" value ="Next" />
 }

ParentViewModel

public class ParentViewModel
{       
    public int PId { get; set; }
    public IEnumerable<CheckboxItem> FirstCheckboxList{ get; set; }
    public IEnumerable<CheckboxItem> SecondCheckboxList{ get; set; }
    public Int64 FSelected { get; set; }
    public Int64 FUniverse { get; set; }
}

CheckboxItem : child view model

 public class CheckboxItem
  {
    public int Id { get; set; }
    public string Text { get; set; }
    public bool Checked { get; set; }
  }

controller action

   [HttpPost]
    public ActionResult MyCheckboxView(int planid,   ParentViewModel model, string nextBtn)
    {
        // do something
        return View(Model);
    }

checkbox names should be like firstchecboxlist[i].fieldname.. look at the html that is rendered — maxlego
– maxlego, Commented Apr 29, 2013 at 16:00

Community · Accepted Answer · 2017-05-23 12:28:18Z

1

Try changing your viewmodel for the ParentViewModel to use a List<CheckboxItem> instead of an IEnumerable<CheckboxItem>:

public class ParentViewModel
{       
    public int PlanId { get; set; }
    public List<CheckboxItem> FirstCheckboxList{ get; set; }
    public List<CheckboxItem> SecondCheckboxList{ get; set; }
    public Int64 FSelected { get; set; }
    public Int64 FUniverse { get; set; }
}

The model binder needs a data structure like a List or an Array so that it can correctly bind elements at specified indexes. IEnumerable is just an interface and doesn't support indexes like this.

Edit

Also, as a side-note, you don't have to bother with the for loop in your EditorTemplate because MVC can do all this for you. Just change the model type to be @model CheckboxItem, remove the loop and get rid of the id attribute so it looks like this:

@model CheckboxItem
@{        

   <div>
   @Html.CheckBoxFor(x => x.Checked, new { onclick = "GetSelectedFrame()" })
      <span id="Padded">@Model.Text</span>
   </div> 
    }
}

Also, make sure your EditorFor call doesn't supply the EditorTemplate's name, as this messes up the "MVC Magic" (see this question which explains that it automatically iterates the list without the template name and doesn't with the template name):

@Html.BeginForm(){ 
    @Html.EditorFor(m=> m.FirstCheckboxList) 
    @Html.EditorFor(m=> m.SecondCheckboxList) 
}

edited May 23, 2017 at 12:28

CommunityBot

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answered Apr 29, 2013 at 15:36

theyetiman

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6 Comments

kum123 Over a year ago

Thanks for your reply 1. Making List didn’t make any difference. 2. If I take For loop off how , then I will get below error right? The model item passed into the dictionary is of type 'System.Collections.Generic.List`1[CheckboxItem]', but this dictionary requires a model item of type CheckboxItem

theyetiman Over a year ago

I'm sorry the List suggestion didn't work. As for the second point, try changing the EditorFor call by removing the templatename:

@Html.BeginForm(){             @Html.EditorFor(m=> m.FirstCheckboxList)         @Html.EditorFor(m=> m.SecondCheckboxList)                  }

theyetiman Over a year ago

Can you show me the HTML that is generated? There is probably a problem with supplying the id to the checkbox instead of letting the model binder set its own

theyetiman Over a year ago

@kum123 - So are you objects still null when you POST? If they are now fixed please mark this as the answer. Also, that doesn't look like HTML, instead it looks like you've copy and pasted a value from the request object in the Visual Studio debugger. Please edit your question and include the HTML that is output to your web browser (press CTRL-U or right-click > View Source on the page). I will edit my answer to explain why Html.EditorFor() doesn't work when you supply the template name...

kum123 Over a year ago

It worked as you explain, but I will be curious to know. Why it doesn't work, when you mention template name. Thanks for your help.

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