Using a DisplayTemplate (with DisplayFor) for each item in a collection

Question

I have created a DisplayTemplate for a Comment class, and placed it inside Comment/DisplayTemplates/Comment.cshtml.

Comment.cshtml is properly typed:

@model Comment

Then, I have a partial view that takes an IEnumerable<Comment> for model. In there I loop through the collection and would like to use the DisplayTemplate for the Comment class. The view, in its integrity:

@model IEnumerable<Comment>

@foreach (var comment in Model.Where(c => c.Parent == null)) { 
    @Html.DisplayFor(model => comment)
}

However, I get an error on the Html.DisplayFor line:

The model item passed into the dictionary is of type 'System.Int32', but this dictionary requires a model item of type 'System.String'.

How can I invoke the DisplayTemplate for each item in the foreach loop?

Universally

If you change "model" to something like "myCommentModel" in your lambda expression does it work? – Commandment

Thanks Joe, but no, it doesn't. Why would it? What was your rationale behind it? – Universally

Answer 1

Instead of having a view that take an IEnumerable<Comment> and that all it does is loop through the collection and call the proper display template simply:

@Html.DisplayFor(x => x.Comments)

where the Comments property is an IEnumerable<Comment> which will automatically do the looping and render the Comment.cshtml display template for each item of this collection.

Or if you really need such a view (don't know why) you could simply:

@model IEnumerable<Comment>
@Html.DisplayForModel()

As far as the Where clause you are using in there you should simply remove it and delegate this task to the controller. It's the controller's responsibility to prepare the view model, not the view performing such tasks.

Percolate

Hah! Brilliant! I didn't know DisplayFor would automatically loop. Got rid of the view too, of course. Thanks! (I agree about the Where clause, I got lazy there for a minute ;) – Universally

@Sergi Papaseit, that's why everytime I see someone writing a loop in a view I always suggest him using templates. – Percolate

Well, I certainly won't forget this one any more :) – Universally

@DarinDimitrov do you have any idea why this is not working in my case #8679302 – Disport

"Or if you really need such a view (don't know why)". DisplayFor can render the list, but it won't render a table. – Diacaustic

Answer 2

While the accepted answer works well most of the time, there are other cases in which we need to be aware of the element's index when rendering (i.e. add custom javascript that generates references to each element based on their index).

In that case, DisplayFor can still be used within the loop like this:

@model IEnumerable<Comment>

@for (int index = 0; index < Model.Count(); index++)
{
     @Html.DisplayFor(model => model[index])
}

Shatterproof

IEnumerable<T> does not support implicit indexing with [i]. Logically then, you would try to use model.ElementAt(i) but then you get an error, so you can only do this by using Comment[] as the model type or model.ToArray()[i] – Outgroup