Modelbinding IEnumerable in ASP.NET MVC POST?

Question

Is there any issues with modelbinding IEnumerable types to an MVC POST?

Some properties in my Model are not being bound upon a post to an action. Seems that properties on the model like strings are ok, but my IEnumerable is what is not being bound.

Here's a snippet of my code:

<%: Html.TextBoxFor(m => m.ResponseInfo.SubsetInfo.Test) %>
    <% for (int i = 0; i < Model.ResponseInfo.SubsetInfo.BandAvailabilities.Count(); i++)
    {%>
        <%: Html.TextBoxFor(m => m.ResponseInfo.SubsetInfo.BandAvailabilities.ToArray()[i].BandName) %>
  <% } %>

And here is what those properties look like in the model:

public IEnumerable<BandAvailabilityInfo> BandAvailabilities { get; set; }
public string Test { get; set; }

The view works fine and outputs a list of textboxes with the expected values in them. But the post Action which gets fired only recognises the Test string as a property. The model state does not contain my IEnumerable data either.

Answer 1

Model binding depends upon how generated html looks like. for ur particular scenario to bind properly html should look like

<input type="text" name = "ResponseInfo.SubsetInfo.BandAvailabilities[0].BandName"/>
<input type="text" name = "ResponseInfo.SubsetInfo.BandAvailabilities[1].BandName"/>
<input type="text" name = "ResponseInfo.SubsetInfo.BandAvailabilities[2].BandName"/>
.
.
<input type="text" name = "ResponseInfo.SubsetInfo.BandAvailabilities[n].BandName"/>

i have not tried it but i am almost certain that call to ToArray method in loop is keeping the system from generating proper names for nested inputs. There are couple of things you can do to remedy this First, in your view model change

public IEnumerable<BandAvailabilityInfo> BandAvailabilities { get; set; }

to

public IList<BandAvailabilityInfo> BandAvailabilities { get; set; }  //or Array

so you don't have to call ToArray method in the loop and proper names are generated for inputs. Second, make an editor template and put it in Editor templates folder either under the current controller or in shared folder's Editor template folder. Make this view accept model of type BandAvailabilityInfo and name of this view should also be BandAvailabilityInfo. then in your main view you only have to replace entire loop with

 <%: Html.EditorFor(m => m.ResponseInfo.SubsetInfo.BandAvailabilities%>

and rest will be handled by framework itself

Answer 2

It works fine with the IEnumarble type.
I think the problem is the ToArray you are writing inside the For loop. (It's very not efficient either)
change the for loop to foreach.

See this excellent answer how to achieve it.